^ A sensible approach. If you get the per-shuttle price that low in your calculations, then it's probably worth it. They are mostly die-cast. How often have you spent that much money for a Trek model of similar size but plastic (e.g. Furuta, Micro Machines, or Johnny Lightning)?
Er...never? :P
The only shuttle I have from any other manufacturer is the Running Press Galileo, which is amazing for just £7.99. I haven't purchased any ships by another other manufacturers for years and years - got my micromachines when I was a lot younger, years ago. Only other ships are the Playmates battle damaged Enterprise D and First Contact E, again from years ago (late 1990s).