IP addresses are supposed to be free! The RIRs are in the business of handing out addresses to whoever applies for them if the applicant can show that they have a reasonable use for the addresses. But as the IPv4 addresses eventually run out, AWS will then buy addresses directly from whoever has them. This is allowed, but a bit dubious, since if someone aren’t using their addresses, it would make more sense to return them to the RIR to be reassigned. But if AWS owns all the addresses, and nobody can get any more, it makes sense for AWS to start charging for the addresses. It would also make sense for AWS to halt and delay any IPv6 adoption, so we should watch for that.