Eric texted his wife from the booth one Saturday with one number: $1,840 this week! She replied with three smiley faces and a question—how much of that did he actually keep? Eric did not know. He had been celebrating revenue. He had not run profit.
Revenue is the loudest number in any reselling dashboard. Platforms display it. Group chats brag about it. Tax forms report it. But revenue is a vanity figure once you understand what really sits between gross sales and the dollars that hit your bank account. Here is the cost stack Eric mapped that week, the four layers that ate his number, and why net profit is the only metric worth optimizing.
The $1,840 That Wasn't
Eric's $1,840 in gross sales for the week came from 34 booth items, 6 eBay sales, and 11 Poshmark sales. Looks great. Now layer the costs.
| Line | Amount | Notes |
|---|---|---|
| Gross sales | $1,840 | 34 booth + 6 eBay + 11 Poshmark |
| Platform fees + processing | −$214 | Mall commission, eBay FVF, Poshmark take |
| Shipping cost (he paid) | −$98 | Above what buyers paid; underpriced labels |
| Cost of goods sold | −$742 | Item-level landed cost from his log |
| Supplies, mileage, packing | −$86 | Tags, tape, gas to drop-off |
| Net profit (excl. labor) | $700 | 38% of gross |
$1,840 in revenue. $700 in net. He kept 38 cents per dollar—not bad for his mix, but a far cry from the figure he had been mentally banking. And the gap was made of four different layers, each invisible from the dashboard view.
The Four Layers That Eat Revenue
1. Platform Fees and Processing
Every channel takes a cut, but the structure differs:
- eBay: roughly 13–14% final value fee plus payment processing (managed payments). Store subscribers receive small basis-point discounts and free insertion allotments.
- Mercari: 10% selling fee on the item price (as of Jan 2025; verify current rate).
- Poshmark: $2.95 flat on sales under $15; 20% on sales $15 and above.
- Antique-mall booths: 5–15% commission depending on the model.
- Whatnot: ~8% on most categories plus processing (varies by promotion).
None of these are unreasonable. All of them stack against the brain's belief that the listed price equals the deposit.
2. Shipping Underpricing
If buyers paid $4 for shipping and your label cost $5.30, you ate $1.30 silently. Eric's week showed $98 of underpriced shipping—almost all from heavy items he had not weighed before listing. Aggregate that across a year and shipping is sometimes the single largest under-tracked margin leak.
3. Cost of Goods Sold
Item-level COGS is where the gap between vanity and reality opens widest. Average-cost thinking ("I usually source at 30%") is fiction. Some weeks you pay 18%. Some weeks you pay 52%. Without an item-level log, you cannot tell which categories are funding you and which are quietly losing money.
4. Operating Costs
Supplies, mileage, packaging materials, insurance, software, the bin of newspaper you actually paid for last week. Each is small. Together they routinely run 5–10% of gross for active sellers.
Why Revenue Optimization Backfires
"I'll just sell more" sounds reasonable. It usually is not, because every dollar of new revenue also drags every dollar of cost with it. If your week's cost stack consumes 60 cents per dollar, pushing revenue from $1,840 to $2,400 also pushes costs from $1,140 to $1,440—the absolute profit grows, but the per-hour math may not, especially if the extra revenue comes from lower-margin items or longer hours.
The healthier framing: net per hour. Eric's $700 net divided by his ~28 hours of work that week was $25/hour. He has used that single number to grade weeks ever since. A "$2,200 revenue week" that took 50 hours is worse than his $1,840 week, not better—even though the headline looks loud.
Revenue is the scoreboard the platform shows. Net profit per hour is the business.
The Numbers Resellers Lie to Themselves About
- "My COGS is about 30%." Verify with item-level data; it usually is not.
- "Fees are basically the same everywhere." They are not. A platform comparison frequently shifts which channels are profitable for a given price band. For details, see Platform Fee Comparison: eBay vs Poshmark vs Mercari.
- "Shipping pays for itself." Sometimes. Often not, especially over 16 oz.
- "I'll add up the supplies at the end of the year." By then they are unrecoverable in your memory.
The Definition Worth Memorizing
Resellers benefit from three distinct profit numbers:
- Gross profit = Sales − COGS. Useful for category-level analysis.
- Operating profit = Gross profit − Operating expenses (fees, supplies, shipping, mileage). Useful for monthly P&L.
- Net profit = Operating profit − Tax reserve (and labor if you assign yourself a wage). Useful for life decisions.
Most platforms display Sales. A few display Sales − Fees. Almost none display Sales − Fees − COGS, and that is the line that actually matters.
What to Do This Week
- Pick one week. Run gross sales, fees, shipping cost, COGS, and supplies.
- Compute net profit. Divide by hours worked.
- Mark the number on your calendar. Compare to next week.
- Stop comparing weeks by gross. Compare them by net per hour.
Eric's first month of tracking net per hour produced one immediate change: he stopped listing items under $12 unless they were trivial to ship. The math told him those listings ate more time than they paid him, and his net per hour climbed from $25 to $34 the next month with no new sourcing changes—just a clearer lens.
Revenue feels great. Net profit pays the bills. The first is the headline. The second is the business.