Yes, it's an issue of price gouging as well. If a basic plan is say 10TB/mo for $100, then overages shouldn't be allowed to be greater than $10/TB. In general plans should have to be a linear (or sublinear) combination of connection fee and data used.

(Not that I have a dog in this fight. Municipal fiber ftfw. Unless you live somewhere that already has 3+ competing providers, the only question you should be asking is "what will it take?")