When I built my Saturn, I thought I could do it for $8K, including the car, just for the basics. I was wrong. Even after I budgeted everything out, all the little stuff kept getting to me. New stock lower control arms because the old ones were shot. New CV joints because the old ones were shot. Etc.

If the car had been brand new, sure, $7K for the cage, firebottle, seat, and other required stuff is possible, but if the car isn't new...

(Geez! This really doesn't sound like me. I LOVED building my car. I know every nut and bolt on that car and know who to blame when it fails. I think I've just accepted the fact that building the car cost me more money in the long run than just buying one used. Of course, that doesn't stop me from delusions of grandeur about building my own FC or C/DSR...)