Profit fell 18 percent on a 40-SKU catalog, and six products account for about two-thirds of the drop: three where new ad spend bought sales at a margin below its cost, two that moved into a higher fulfillment fee band after a packaging change, and one whose return rate more than doubled. The other 34 SKUs lost a little volume and otherwise behaved. Below is the full decomposition, with every figure shown so you can rebuild it on your own data. The numbers are illustrative and belong to no customer.
Take an Amazon seller with 40 SKUs in Home and Kitchen, where Amazon's published referral fee on sell.amazon.com is 15 percent. Fulfillment fees are illustrative. Both months are built from settlements reconciled at the transaction level and cut to order date, so the boundary days are in the right month. That step matters more than any other; the general method is in why am I down in profit this month.
June
July
Check June: $210,000 minus $78,000 minus $31,500 minus $36,400 minus $16,800 minus $6,300 minus $2,500 equals $38,500. Check July: $208,000 minus $77,300 minus $31,200 minus $38,150 minus $19,400 minus $7,900 minus $2,480 equals $31,570. The drop is $6,930, and $6,930 divided by $38,500 is 18.0 percent, on revenue down less than 1 percent.
Sum: minus $2,000 plus $700 plus $300 minus $1,750 minus $2,600 minus $1,600 plus $20 equals minus $6,930. It ties, so no line was dropped.
Three lines carry the damage. Ad spend is $2,600, fulfillment $1,750, refunds $1,600: $5,950 of the $6,930. The revenue dip is real but small, and COGS and referral fell with it, as they should.
A cost line is a symptom. The cause sits on specific products, and finding it means holding the SKU-level fee, ad, and refund data that a lump-sum ledger throws away. This is the point where a seller with reconciled SKU-level profit data keeps going and a seller with a blended P&L stops.
Sorting July ad spend by SKU against June shows three products with increases well above the rest. For each, the test is whether the extra attributed sales produced more gross profit (after COGS and fees, before ads) than the extra spend cost.
The three SKUs added $2,650 of spend. The other 37 SKUs cut $50 between them, which is how the total lands at $2,600. Net effect of the three on contribution, counting the sales they bought: minus $1,607.
July's per-unit fulfillment fee by SKU, compared to June's, shows two products whose fee stepped up while units held flat.
Together, $1,705 of the $1,750. The remaining $45 is mix across the other 38 SKUs.
Refund units by SKU in July against June show one product out of pattern.
Return reasons cluster on "arrived broken." The remaining $368 of refund increase is spread across the catalog at rates within normal range.
The rest of the catalog:
$4,544 plus $2,000 plus $386 equals $6,930. Decomposed to the dollar.
Profit fell 18 percent because three campaigns bought sales below their break-even, two packaging changes raised the fulfillment fee on 1,750 units a month, one product started breaking in transit, and the rest of the catalog softened a few percent.
Each cause carries its own fix. The three campaigns lose money at current margins: cut them or fix the margin upstream. The two packaging changes cost $1,705 a month; either they lift conversion enough to pay for that or they get reverted. The mug set needs a packaging inspection and a claim on any batch that was shipped damaged. The soft volume across 34 SKUs is the only item on the list that might be seasonal, and that is a year-over-year check, not a month-over-month one.
The totals alone would have told you this: revenue flat, profit down 18 percent, costs up. Every action above required the SKU layer.
Ask Crunch, the analytics AI inside ConnectBooks, for a deep dive on why profit dropped this month, and it runs the four steps above across all 40 SKUs: what changed across sales, pricing, ads, fees, returns, storage, inventory, and margins; over the right periods; on which products; why; and what to do next. The example on ConnectBooks' Crunch page follows the same shape, with a decline traced to six SKUs, driven by ad spend without enough incremental gross profit and two products moving into a higher fulfillment fee band. The figures here are different and are offered so you can check the arithmetic yourself.
The data Crunch reads is what makes step 2 possible. ConnectBooks reconciles each Amazon settlement into QuickBooks or Xero at the transaction level, so referral fees, fulfillment fees, refunds, and storage post to their own accounts against the SKU that caused them, with FIFO landed cost per unit alongside.
It cannot tell you that SKU-15's mugs broke because the corrugated divider was dropped from the spec in a cost-down. It sees a return rate and a reason code.
It cannot decide whether SKU-04's retail carton is worth $990 a month for the shelf presence. It prices the fee delta and leaves the trade-off to you.
It cannot see a landed cost you did not record. If SKU-27's last PO is missing inbound freight, its pre-ad margin is overstated, and a campaign verdict built on that margin is wrong in the direction of "keep spending."
It does not pause a campaign, revert a carton, or open a claim. It reports the six SKUs and what it would do about each. The Seller Central login stays with you.
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