I think you may be missing some of the key elements of Musk's vision. The tunnels would be for autonomous, electric vehicles only. Congestion wouldn't exist, each vehicle would travel along at the same speed. This is the same vision above ground, but harder to implement fully for two main reasons: special cases/driving situations exist in many many places, and it's hard to get 100% compliance, as plenty of people aren't ready to give up their manual driving freedom. In these tunnels, it would be standardized and electric only, solving both of these challenges and accelerating adoption.
Layman's opinion here, but of course they'd want to reuse their rockets? Why would throwing away your entire product and having to create again from scratch each time be the ideal?
This would be an iterative process. First, figure out how to successfully recoup the rocket. Second, see what issues exist with the integrity of these rockets, and work to fix those. Try reusing. Find more issues, fix those, etc. Eventually/hopefully, profit?
