Yup some add-ons are pricey, so you have to kind of cherry pick the ones you want, and it's often a good idea to take a look around to see if you can pay less somewhere else.
But if I was some kind of mega-space shuttle fan, then being able to fly the shuttle around whenever I wanted to for about for 25 quid (UK equivalent), would sound like pretty good value to me. And apparently you can do quite a lot with the Shuttle in this add on, I remember reading a review of it in a magazine about a month ago and they rated it quite highly.
I guess like most things, you get what you pay for, and that's the real beauty of Flight Simulator, in that you can add whatever you prefer to it to make it your own. And even if exactly what you want is not available, then you can make it yourself quite easily, so if you wanted to put your own house in FS, you could do it without too much difficulty.
Chock