Yeah the people who RICE them out. Most of the guys that actually modify their car for performance do it themselves. Theres a big difference between a riced out car and a modified one. I mean.. Think about the SCC Cup alone. All the guys in there did their own work on the car. Then again thats for racing so I guess it makes more sense than to do it for fun.

EDIT: And as for the why do people spend 40k on a car like this. Well think about it. You can either spend 40k on a car that other people will be driving. Or spend 40k on a car of your choosing (It could even be an old car from the 80s) and have it look how you want, custom paint, wheels, ect. Not to mention there being a strong chance that it could outperform that other 40k car that everyone will be driving. I'd pick customizing my own car and doing an engine swap over driving a generic car any day.

EDIT EDIT: That... And because I have a very large penis.