Internet service is metered. It's just metered in very large chunks instead of by the penny. Try going over your monthly bandwidth cap and see what happens.

The ISPs have total control over their subscribers' connection fees. If they set them too low to make a profit,* then they need to raise those fees and live with the consequences, not go trying to extort profits from new sources.

*I don't believe for an instant that the major ISPs are actually hurting, mind you. They just see an opportunity to make even more of a profit.