I've thought about this, and the main reason I'll focus on AWS is because it's by far the more popular one. So far what I've seen is that if a seller is advertising MS Azure or Google Cloud, he's also advertising AWS. Chances are those other types of accounts are also fraudulently obtained, so they also qualify.
Its because for AWS accounts demand is much higer than supply and account prices are up. Great oppurtunity for scammers..
What do you mean with "fraudulently obtained" ?
Do you mean violating aws ToS ?
Do you mean providing false information to get these accounts approved ?