Was hoping you'd chime in. When you say they make most of their money on Amazon, is that total $ or is that margin? I'm pretty sure that eBay charges lower commission (I've sold a few textbooks on Amazon the last couple of years and my net take seemed to be at lower % than what I sold on eBay), so I'd think that the higher margin would be selling on eBay. Amazon makes it harder to see competitive sellers, and the seller they showcase/quote on the product page isn't always the lowest price, so maybe sellers can charge a higher price on Amazon. Regardless, I just bought some personal care products on eBay for ~$95. Would have cost $120 on Amazon. I don't sell on Amazon so I don't know much about it but I do know that they charge the seller more in fees (30-40% I believe compared to the roughly 8% it costs me on eBay) and they have a lot more rules for sellers. The sellers I know sell more items on Amazon than eBay and they say it's because Amazon has more users and actually promotes itself.