> Why/how is it free? How much is it typically? Do all/most cities have "backhaul" easily available? Isn't backhaul owned by ISPs as well and basically like a fat pipe?

Sometimes but not always, the Tier 2 internet market is acutally quite competitive and usually you can get fiber from a couple of providers within 50 miles of any location in the US (5 or less if it's reasonably populated). The problem of course is to be an ISP you have to deliver the traffic that last few miles.

This whole thing is further obfuscated by the fact that the entire infrastructure market is very human powered. Few providers provide public maps and in order to find these fiber connections you literally have to know the right people. The internet has automated everything but those people building and maintaining the backbone still need sales calls to tell you where they can connect and a bribe before you get a good price.

You can get connections suitable for backhaul pretty much anywhere as long as you are within reach, or prepared to pay for, a copper or fibre connection to an exchange. It just costs more.

I'm not up to date on prices.

Backhaul is 'just' another connection but without the same contractual restrictions as you'll usually find on normal subscriber connections.

You'll find it used in at least two different ways: as a synonym of transit to talk about a way for your ISP to connect to any other ISP via the provider they get it from, and as a means of having an access provider forward last mile traffic to one or more central locations.

But in both cases it just suggests that you have agreed with a provider to forward traffic for your users on your behalf.

NYC, among very few other places in the US, actually has some insanely good options for business grade (and priced) connectivity. (HFTs pay for very high speed connectivity.) As for why it's free to NYC mesh, I don't know. Pet project of an employee?