SDE, plus one extra line item: inventory
E-commerce businesses (Amazon FBA brands, Shopify stores, dropshipping operations) are valued on the same SDE basis as a conventional operating business, with one addition most operating-business buyers don't have to think about: inventory. Whether inventory is included in the asking price, and at what valuation (cost vs. landed cost vs. a discount for aged stock), is a real, separate negotiating line, not a rounding error.
This site tags a listing's inventory_included status explicitly for exactly this reason: two e-commerce listings at the same headline asking price can carry very different effective prices once inventory terms are compared like-for-like.
What's different about diligence here
Platform concentration (a business built entirely on one marketplace's traffic, versus one with its own site and email list) is a real risk factor, similar in spirit to a media property's platform-policy risk. Supplier relationships, minimum order quantities, and whether the current owner has an exclusive or exportable supplier agreement all affect whether the business survives a change of ownership intact.
Amazon FBA listings specifically carry account-health risk: a buyer is often also acquiring the seller account's standing (reviews, case history), which can be harder to verify than a bank statement.