"Which products lost money last month after fees" is one question with six different arithmetic problems behind it. Amazon takes a referral fee and, for FBA, a fulfillment fee. Walmart takes a referral fee and, for WFS, a fulfillment fee on a different weight schedule. eBay takes a final value fee on the total amount of the sale, sales tax included, plus a per-order fee. TikTok Shop takes a commission and, on affiliate-driven orders, the creator commission you set. Shopify takes payment processing, and shipping is whatever your carrier charged. Temu takes what its settlement shows. Ecommerce analytics AI can answer the question across all six only if someone first put every one of those fee shapes on the same line, with the same cost of goods and the same treatment of returns. That is the work. The AI is the last step.
Fee treatment. "After fees" means something different on each channel. On eBay, per the selling fees page on ebay.com, the final value fee for most categories is 13.6 percent of the total amount of the sale up to $7,500, plus $0.40 per order over $10, and the total amount includes item price, shipping collected, and sales tax. On Amazon, per sell.amazon.com's pricing page, Home and Kitchen carries a 15 percent referral fee with a $0.30 minimum, and fulfillment is separate. On Walmart, per marketplace.walmart.com's pricing page, Home, Kitchen, Decor and Garden also carries 15 percent, computed on a total that includes shipping and handling, with WFS fulfillment priced by shipping weight. A margin comparison that treats "fees" as one bucket per channel hides the fact that eBay's fee base includes tax you never kept and Walmart's includes shipping the customer paid.
Shared COGS. A SKU has one landed cost per FIFO layer, regardless of where it sold. If the Amazon dashboard has $7.60 typed in, the Shopify app has $7.10 from last year, and the TikTok spreadsheet has nothing, the three "margins" are three different fictions. The question requires one cost basis applied to every channel's units in the same period.
Channel-tagged returns. A refund on Amazon returns most of the referral fee. A refund on eBay may earn a fee credit under eBay's fee credits policy. A return on Shopify costs you a label. A TikTok Shop return on an affiliate order raises the question of whether the commission comes back. If returns are booked as one lump in a "refunds" account, the SKU that bleeds on one channel is invisible.
Illustrative numbers. Fee percentages are the published rates named above; fulfillment and ad figures are illustrative. Take a 32-ounce insulated water bottle, landed FIFO cost $7.60, priced at $24.99 on Amazon (FBA), Walmart (WFS), and eBay (seller-fulfilled, free shipping). August.
Amazon, 600 units
Walmart, 220 units
eBay, 90 units, one unit per order
Same product, same price, same cost. Walmart is the best channel for it this month, Amazon is the volume channel, and eBay is thin because a $6.85 label and a fee computed on tax you never kept eat a $24.99 price.
Now the SKU that answers the question. The seller also sells a 12-ounce kids' bottle at $14.99, landed cost $4.90. On eBay the per-unit fee is 13.6 percent of $16.04 plus $0.40, or $2.58. The label is still $6.85. Contribution per unit before ads and returns: $14.99 minus $2.58 minus $6.85 minus $4.90 equals $0.66. Add $1.20 per unit of promoted listing fees and a 5 percent return rate, and the SKU loses money on eBay while making 21 percent on Amazon. The fixed dollars in eBay's fee shape (the per-order fee, the label) do not shrink with price. That is the product to pull from eBay or reprice, and it is invisible in a blended "eBay margin" figure.
Crunch, the analytics AI inside ConnectBooks, answers plain-language questions from reconciled data and returns the products behind the figure with the reason each one moved. Asked which products lost money last month after fees, it finds what changed across sales, pricing, ads, fees, and returns, compares the periods you name, isolates the SKUs, explains the cause, and recommends a next step. The Crunch page names Amazon, Shopify, Walmart, TikTok Shop, and eBay as the channels it reads. ConnectBooks itself syncs six sales channels, Temu included; the integrations page lists them and the accounting systems each one pairs with.
The reconciliation underneath is what makes the answer possible. Each channel's settlement or payout posts to QuickBooks or Xero at the transaction level, fees split by type, refunds tied to orders, FIFO COGS applied per unit from one cost basis. The profit reports show contribution by SKU and by channel on that basis, and the comparison report puts two periods or two channels side by side. In the example above, the kids' bottle shows up as an eBay loss because the eBay fee, the label, and the return each posted against it, and the same $4.90 cost applied on every channel.
It cannot fix fee treatment it was never given. Feed it a Shopify export where "fees" means processing and an eBay export where "fees" means a percentage of tax-inclusive totals, and it will compare them as if they meant the same thing.
It cannot invent a shared cost basis. If the kids' bottle has no landed cost on TikTok Shop, the AI either flags the gap or computes a fake margin. Ask which it does before you trust it.
It cannot split a brand ad campaign across channels. A paid social campaign that lifted Amazon searches and Shopify orders in the same week has no clean attribution, and any allocation the AI proposes is an assumption, not a measurement.
It cannot know the kids' bottle is being kept on eBay to clear a discontinued colorway. It sees a loss and recommends a fix. The decision to hold it anyway is yours.
It cannot take the SKU down. The eBay login stays with you.
Run the arithmetic on one SKU across your channels by hand. If the three contribution figures differ by more than you expected, the cause is almost always one of the three things above, and it was there before any AI looked at it.
Running an e-commerce business comes with plenty of challenges, but ConnectBooks is here to make your life easier. With real-time insights, seamless integrations, and detailed tracking of your profitability and inventory, you can stay ahead of the game. Whether you’re selling on Amazon, Shopify, Walmart, TikTok or eBay, ConnectBooks helps you manage your finances with 100% accuracy and confidence, so you can focus on growing your business.
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