There are always costs to projects (money spent on wages to UK taxpayers, money spent on imports, environmental damage, political damage from nimby campaigns, opportunity costs from people working on this project instead of another one - say crossrail 2)
There are always benefits to projects (money generated from more passengers, benefit of more space on existing lines, movement of freight from road to rail, movement of passengers from air to rail, benefits politically from spending money outside of London)
This is the same no matter what project, or who is funding it. Musk presumably includes "being able to go to Mars in his lifetime" as a benefit of starship, as that's his stated goal.
You could reduce the cost if you said "we don't need to go to mars", but that would remove the main benefit, and Musk isn't going to put as much as he does into it.
Clearly if you can reduce costs without reducing benefits it will increase the viability of a project, but reducing costs on its own does not necessarily increase the viability.
Reducing costs gives two benefits. First the polical opposition has less to complain about. Second, if you reduce costs you can build more for the same money. In transit networks effects are critically important. The more places you can get to (given time, cost, safety, comfort...) the more likely you are to use it. Thus cheap drives better to a large extent.
There are always costs to projects (money spent on wages to UK taxpayers, money spent on imports, environmental damage, political damage from nimby campaigns, opportunity costs from people working on this project instead of another one - say crossrail 2)
There are always benefits to projects (money generated from more passengers, benefit of more space on existing lines, movement of freight from road to rail, movement of passengers from air to rail, benefits politically from spending money outside of London)
This is the same no matter what project, or who is funding it. Musk presumably includes "being able to go to Mars in his lifetime" as a benefit of starship, as that's his stated goal.
You could reduce the cost if you said "we don't need to go to mars", but that would remove the main benefit, and Musk isn't going to put as much as he does into it.
Clearly if you can reduce costs without reducing benefits it will increase the viability of a project, but reducing costs on its own does not necessarily increase the viability.