I know what u guys mean about building your car yourself. I think that even if you do pay somebody else to do the work for you, you still get that satisfaction out of it that you wouldn't quite get when u buy a car with all the mods already done.
Right now, my car is pretty stock and im slowly getting one mod at a time, and when you realise how long it takes to get each mod, the more you appreciate it. Plus the feeling of having a new mod after waiting months is def something you dont experiance with a car brought. Dont get me wrong, it is definatley a better economical reason to buy a built car, you are going in to save heaps. Selling your car that you have built, in the end your never gonna get your money back.
So really i think your paying for the experience of the feeling that you get of having one mod at a time when doing your own car... if that makes sense... Oh i forgot to mention that you learn much more this way, especially when you dont know much about cars (like myself), you realise how each mod affects your car!