The point about transit to other big cities is another interesting possibility, and I could imagine that as a path to bootstrap a city's own economy. If this hy

The point about transit to other big cities is another interesting possibility, and I could imagine that as a path to bootstrap a city's own economy. If this hypothetical new city was ~30 min from somewhere like downtown SF or the Google campus via a high speed rail (admittedly a huge "if", given the poor track record of getting high speed rail or really any new rails built in the US in a reasonable timeframe), I think you could get a lot of people to move there for cheaper housing and commute to work. Then you could (somewhat simultaneously) get restauarants, bars, grocery stores, a hardware store, etc. to open in the new city to serve the new residents. Once there are a lot of people living there (and, importantly, the area is widely accepted as cool and up-and-coming), startups and other companies would have incentives to move there or open offices there. This basic process seems to have played out in places like downtown Oakland and in DUMBO and Greenpoint in Brooklyn in recent years. But Brooklyn and Oakland both have their own rich histories and existing neighborhoods and economies, which keeps them from evolving quickly, and big changes can cause big problems like gentrification. It's definitely a moonshot idea but I can imagine this process being even more successful, and avoiding some of the biggest drawbacks, in a new city.