Something tells me they can get away with paying a bit less and still attract experienced candidates who would like to work at a small company with a mission they believe in while working in their preferred language/framework.
I mean, I'm a developer in Denver writing Rust and get paid $265k. $90k-$110k is what the body shops writing Java that won't ever work the way it's supposed to written by fresh bootcamp grads for a new insurance company every six months pay out here.
Built in Colorado is sort of a front for the VCs here; I don't trust those numbers, knowing the salary of about 40 or so engineers out here in 20 different companies.