"Last mile infrastructure just costs too much and you can't have umpteen different companies digging holes in the street and stringing wires."
If you remove all the regulatory overhead last mile is cheap, something on an order of $100 per customer in urban areas.
I understand you just through out a number but you're at least an order of magnitude off. This is an article which is about 7 years old. I can guarantee you the prices have not lowered since then.
https://arstechnica.com/tech-policy/2010/03/fiber-its-not-al...
I've said for a while that we could rely on a free market solution to the broadband market with one very large change from the way that things are done now. Last mile infrastructure should be publicly owned and customers should be allowed to choose any provider. Once that's the case, then you can have a truly competitive market that's more likely to give consumers choice. Short of that, heavy regulation is better than allowing monopoly/duopoly players to behave in whatever way they want.