"I think our experience with the shuttle has shown that the calculation is more complicated than it first appears. A re-useable spacecraft makes sense on paper, it doesn't have to be rebuilt from scratch each time you use it. On the other hand, it has to be designed to be used many times and to last a long time, and it requires a large maintenance infrastructure."

I think you look at the shuttle, you must ask, in terms of weight [mass] how does a Shuttle compare. On Shuttle the only part which can be called re-useable is the Orbitor- or as most call it the Shuttle:
" Gross Mass: 99,318 kg (218,958 lb). Empty Mass: 99,117 kg "
http://www.astronautix.com/lvs/shuttle.htm

If your purpose is to get crew cheaply into orbit and return them, it's quite hideous [I'll not address it's other purposes].

Let's compared to Gemini: Mass: 1,983 kg (4,371 lb).
http://www.astronautix.com/craft/gemini.htm
Gemini wasn't re-useable- wasn't designed to be. And held only 2 crew instead 7. But it got the crew to orbit and returned them. If you simply times the mass of Gemini by 4 [17484 kg] you get 8 crew capacity- one should be able to easily make one non-reusable module which crews 7 which would less than 17,484 kg that gets crew up to orbit and down again. The cost of making the shuttle could be said to be 80% of it's total weight. If your sole purpose was to get the crew into orbit and return them. But of course the Shuttle didn't have this sole purpose [despite it's name] and it's numerous purposes were part of it's problem.

The costs of making spacecraft reuseable in the space environment would be much less costly for number of reasons- assuming one has modest goals in terms of reuseablity and keep a vehicle limited a narrow purpose. A lunar lander may be designed to used say 20 or 30 times requiring little in terms of servicing [other than refilling it] and then perhaps require a major overall or simply scrapped. With experience one could improve upon the design or one could have facilities in which significant maintance can be performed.
Of course one shouldn't regard scrapping a vehicle as throwing it away- parts could robbed from it and material melted down or in other ways used.