Fred J. McCall wrote:

They're called 'fixed costs' because they're FIXED. They don't change
no matter what your flight rate is.


I think this is an over-simplification. If your ground infrastructure
is setup to handle X flights per year and this requires that one shuttle
enter maintenance phase before another one is finished, it means that
you need 2 maintenance bases, and enough employees to process 2 shuttles
concurrently (or even more if a 3rd shuttle is in a heavy maintenance
phase monopolising a maintenance bay and employees for months/year)

Lower the launch rate to a point where shuttle #1 has fully exited the
maiintenance facility by the time shuttle #2 lands, and it means that
shuttle#2 can use the same facility and staff that have worked on
shuttle #1 just before.

In other words, once NASA is given the order to plan for no more than
say 3 launches per year for Shuttle, it could then scale its ground
infrastucture down. But as long as it has dreams of 12 launches per
year, NASA will keep ground infrastructure scaled up to handle the
remote possibility of 12 launches per year, even if in reality, it may
never do more than 6.

So I think there is room to significantly reduce ground costs after
assembly complete if NASA is told to not plan for more than 2 or 3
shuttle launches per year allowing it to scale down its ground
infrastructure.