Stories of how Amazon bullied its providers into giving better payment terms while at the same time taking as long as possible to pay what it owes are legendary. In particular, there were long periods in the past where Amazon managed positive cashflow while keeps earnings at zero.

I never connected the dots that Amazon used the same tactics on its customers. I just bought a book (Rust book if case you're curious) and afterwards noticed that it was a kindle book. I swear it must've taken be 3-5 seconds to press the return button. I decided to talk to customer support to make sure I had actually returned (it wasn't obvious at all, in particular ebook returns don't show up in the list of "all returns"). Anyway, I talked to customer support and they helpfully confirmed that I had indeed initiated the return and I would have the money back in 5-7 working days. So it took them <3 seconds to take my money, but to have it back it takes 5-7 working days. This is intentional.