I don't use Ebay, but don't some of those fees cover the taxes? I mean, as far as I know if you're selling something on Ebay, the taxes are considered paid, it's all legal. I also came accross this discussion that seems to confirm my hypothesis. So my point is, it's not only Ebay getting rich from the fees they impose (even though they are), but it's also the fees associated with the whole buying-selling business their fully legal. Darkweb markets are obviously not paying taxes (right?), and if a version of ebay accepted cryptos and did everything to remain legal, it would probably impose fees like that as well.