You don't need more tunnels -- you just limit your passengers to your most profitable, and make a luxury transit system rather than a mass transit system. This

You don't need more tunnels -- you just limit your passengers to your most profitable, and make a luxury transit system rather than a mass transit system. This is what Tesla did by starting with the Tesla Roadster then Model S then Model 3... and it's what the Hyperloop aims to do. Launch as a small throughput luxury product and if it's profitable then it doesn't matter if it ever expands beyond that or not.