Even if they were one-shots, I think it'd be cheaper to build a whole bunch and use them then try to maintain three or four. It costs a lot of money to refurbish the shuttle between flights.
Reading these comments, it sounds like people (in general, not just the commentors) just don't get it. The goals are there. The adventure is there. They're designing the systems now. What's missing? Why aren't people (again, in general) more excited about human spaceflight?