It's easy enough to realise that you're always selling less (computing power) than you pay for. The margins are inevitably small, but there are other reasons to

It's easy enough to realise that you're always selling less (computing power) than you pay for. The margins are inevitably small, but there are other reasons to get in the business. For Amazon.com the main reason was probably to build such a huge economy of scale that they don't need to buy extra capacity in Q4.