So we get mod tools in the end.

[a completely inoffensive name]

You mean similar to AppStores on smartphones nowadays?
With similar prices (mostly ranging from 1-6€) I'd not be against that but I'm afraid companies that ask 2$ for one-new-skin-awesome-DLC-buy-now-! would want quite a lot of money for that, 30% of a dollar not being enough etc.

30% of a dollar from 1,000 or 5,000 or even 10,000 adds up. Especially for people who would have just made the mod for free in the first place if there wasn't the system put in place.