[pas]

No (no fundamental reason). Yes (same or higher).

Also, AWS costs a lot just in traffic. A lot of people store things on S3 and then make that publicly available.

AWS is "da cloud" for a lot of people. So they ride that wave high and mighty, charging a lot for everything they can easily measure. People will just pay it and will try to [post-]rationalize how it's cheaper than other providers, because AWS is better.