It's not a purchase, it's a rental with the entire rent paid up front. You know it's a rental because you enter into a continuing contract with them, which causes the games to be returned when either party breaks the contract. You have to map your mental model to view it that way, and put a matching value on things. It's why i only 'buy' games on steam when they're steeply discounted because that's the only time they're fairly priced.

Anyway, at some point this is going to get regulated, especially in the EU. They won't be allowed to use terms like 'purchase' and 'buy' without a specific legal consequence (like the right of resale). Until then we can only hope they get onerous enough to get on the radar of lawmakers.