The Real Costs of Reselling: What a Year of Tracking Every Penny Revealed

Most resellers overestimate their profit. Not by a little — by 25 to 40%.

That’s the finding from London-based software developer Oleksandr Prudnikov, who spent a year tracking every single item his wife bought and sold as a reseller.

Every car boot sale entry fee. Every gallon of gas. Every padded envelope and roll of tape.

And the numbers told a very different story than what we expected.

If you resell as a side hustle — whether you source from garage sales, thrift stores, flea markets, or charity shops — this is probably happening to you too. Here’s what a year of obsessive tracking revealed about the real costs of reselling.

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The Problem: Revenue Is Not Profit

Oleksandr’s wife started reselling about 18 months ago. She’d go to car boot sales (the UK version of garage sales — massive outdoor markets where hundreds of people sell from their cars) on Saturday mornings, buy 10 to 15 items, then list them on eBay and Vinted during the week.

After a few months, she was bringing in around $600 to $800 a month in sales.

It felt like a solid side hustle. But when Oleksandr looked at their bank account, the numbers didn’t add up. The balance wasn’t growing the way the sales figures suggested it should.

“The issue was simple,” he says. “She was tracking revenue, not profit. And the gap between those two numbers is where most resellers lose money without realizing it.”

The Costs Nobody Talks About

Every reselling YouTube video and TikTok shows the buy price and the sell price. “Bought this for $5, sold it for $40!” That’s $35 profit, right?

Not even close. Here are the costs that sit between revenue and actual profit.

Platform Fees

This is the one most people know about, but still underestimate.

eBay charges around 12-13% of the total sale including shipping in the US, and 12.8% in the UK.
Mercari takes 10%.
Poshmark takes 20% on sales over $15.
Vinted charges the buyer, so no seller fee (this is why Vinted sellers tend to have better margins).
Facebook Marketplace is free for local pickup, but charges fees for shipped items.

On a $40 eBay sale, that’s roughly $5 in fees. Already your $35 “profit” is down to $30.

Shipping and Packaging

This is the silent killer of reselling margins.

A standard shipping label runs $4 to $8 depending on size and weight. A padded envelope costs $0.50 to $1.50. Boxes, tape, tissue paper — add another $1 to $2 per item if you’re packaging things properly.

That’s $5.50 to $11.50 per item in shipping and packaging costs. On our $40 sale, we’re now looking at maybe $22 in “profit.” And we haven’t even started counting the costs that most resellers completely ignore.

Sourcing Costs (The Hidden Ones)

This is where the real leakage happens.

Entry fees. Car boot sales and flea markets charge buyers an entry fee. In the UK it’s typically $6 to $18 per visit. Garage sales are free, but estate sales and flea markets often charge admission in the US, too.

Gas and transportation. My wife drives 20 to 40 minutes each way to the better car boot sales. That’s $8 to $15 in gas per trip. If you’re hitting thrift stores across town, you’re spending gas money whether you realize it or not.

Pro Tip: Make sure to track and deduct your mileage on your taxes.

Parking. Some flea markets and thrift store areas charge for parking. Small amount, but it adds up weekly.

Here’s the key insight Oleksandr stresses: these costs need to be split across everything you bought that day.

If you paid $12 to get into a flea market, spent $10 on gas, and bought 10 items — that’s $2.20 per item in shared sourcing costs on top of what you paid for each one.

“Most resellers never make this calculation,” he says. “They treat entry fees and gas as invisible costs that somehow don’t count.”

The Real Math on a “Great Flip”

Here’s a real example from Oleksandr’s tracking data.

His wife bought a Le Creuset casserole dish at a car boot sale for $10. Sold it on eBay for $55. Looks like $45 profit on paper. Here’s the reality:

Cost	Amount
Purchase price	$10.00
Share of entry fee ($12 ÷ 12 items)	$1.00
Share of gas ($9 ÷ 12 items)	$0.75
eBay fees (12.8%)	$7.04
Shipping label	$6.50
Packaging (box + bubble wrap)	$1.80
Total costs	$27.09
Actual profit	$27.91

Still a great flip. But it’s $27.91 — not the $45 most people would claim. That’s 38% less than the initial calculation.

Now multiply that gap across 40 to 50 items per month. You could be overestimating your monthly profit by $200 to $400.

Over a year, that’s potentially $3,000 to $5,000 in imaginary profit.

What a Year of Data Actually Showed Us

Being a software developer, Oleksandr responded to his wife’s spreadsheet chaos the way developers do — by building a free iOS app to track reselling profits. It’s called FlipperHelper, and his wife has used it to log every item bought and sold over the past year.

Here’s what the data revealed.

Margins by Category

Not all categories are created equal when it comes to the best items to flip for real profit margins.

Kitchenware and homeware (Le Creuset, Denby, KitchenAid): 40-55% net margin. Best category by far. Items are sturdy, easy to ship, and buyers pay premium prices for known brands.
Vintage and branded clothing: 25-40% net margin. Volume is there but shipping costs more (heavier, needs careful packaging), and return rates are higher.
Books: 15-25% net margin. Heavy to ship, low individual profit. Only worth it for specific titles worth $10 or more.
Electronics: Highly variable. 50% plus when it works, but higher risk of returns, defects, and dead stock.
Toys and games: 35-50% net margin. Highly seasonal — Christmas does significantly better than other times of year.

The Sell-Through Problem

Here’s something else the data surfaced that rarely comes up: not everything sells.

Oleksandr’s wife has a sell-through rate on clothing of about 70%. That means 30% of what she buys in that category never sells.

Those items represent pure cost — purchase price plus their share of sourcing costs, with zero return.

“When you factor in unsold inventory, your effective margins drop further,” Oleksandr explains. “That $4 jacket that didn’t sell isn’t just $4 lost — it’s $4 plus its share of entry fees and gas, plus the time spent listing it, plus the storage space it took up for months.”

Which Sourcing Locations Actually Pay Off

This was the most surprising finding. Some car boot sales feel busy and exciting but don’t actually produce profitable stock. Others feel quiet but consistently deliver high-margin finds.

Without tracking, you’d never know the difference. You’d keep going back to the “fun” markets instead of the profitable ones.

After six months of data, Oleksandr’s wife shifted her routine — she dropped two car boot sales with poor return-on-trip numbers and added a charity shop route that consistently produced better finds.

Her average monthly profit went up about 20% from that one change alone.

How to Start Tracking (Without Making It a Job)

You don’t need an app to start tracking. You just need a system that takes less than 15 seconds per item, because anything slower won’t stick.

The Minimum Viable Tracking System

For each item, record:

What you bought — a photo is fastest
Purchase price — what you actually paid
Where you bought it — which market, store, or sale
Date — so you can calculate days to sell later

For each sourcing trip, record:

Entry fee (if any)
Gas or transport cost
Number of items bought (to split shared costs later)

For each sale, record:

Selling price
Platform (for fee calculation)
Shipping cost
Packaging cost

The Tool Doesn’t Matter (Much)

A Google Sheet works if you’re disciplined. A notes app works if you’re very disciplined.

Oleksandr built FlipperHelper because his wife needed something she could use standing at a car boot sale in the rain, with one hand holding a coffee. It tracks all of the above, works offline, and does the math automatically.

But as he’s quick to point out, the tool matters less than the habit.

“Whatever system takes the least effort is the one you’ll actually use consistently. The people who get in trouble aren’t the ones who chose the wrong app — they’re the ones who tracked nothing for six months and tried to reconstruct it from memory.”

The Quarterly Check-In

Even if you track religiously, the data is useless if you never look at it. Set a reminder once a quarter to sit down and review:

What’s your real profit margin by category?
Which sourcing locations produce the best returns?
What’s your sell-through rate? Is dead stock eating your margins?
Are shipping costs trending up? (They usually are.)
Are you actually making enough per hour to justify the time?

That last question is uncomfortable but important. If you’re making $300 a month profit but spending 40 hours on it, that’s $7.50 an hour.

The tracking data tells you whether you’re running a good side hustle or an expensive hobby.

The Tax Angle

In the UK, you get a £1,000 ($1,250) tax-free trading allowance. In the US, platforms now report to the IRS if you exceed $2,000 in sales.

Either way, having clean records of your actual expenses means you’re only paying tax on real profit — not on revenue.

Every tracked expense reduces your taxable income. That entry fee, that gas receipt, that roll of packing tape — they all count.

At tax time, the difference between “I think I made about $3,000” and “I have records showing $3,000 in revenue and $1,800 in documented expenses” is real money.

What Every New Reseller Should Know

Oleksandr’s advice is simple: start tracking from your very first purchase.

Not next month.

Not “when things get serious.”

Day one.

“The biggest regret my wife has isn’t a bad buy or a missed flip — it’s the first four months she didn’t track, when she has no idea whether she actually made money or just shuffled it around.”

You don’t need to be obsessive about it. You need to be consistent. Log the buy, log the sale, log the costs. Ten seconds per item at the point of purchase. Then once a quarter, sit down and look at what the numbers are telling you.

The resellers who last aren’t the ones who find the best stuff. They’re the ones who know their numbers. Everything else follows from that.

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