I can third that on the amount of money you put into an old car. My project/daily driver is a 94 Acura Integra, B18B 1.8 liter, about 130 - 150 horse (depends on the gas I run, temp outside, etc.), I have a hi-flo header, dual exhauset (yes, I know, dual on a 4 banger, smoke comes out of both pipes when it gets cold so i dunno), performance clutch, and 215/40ZR-16 tires in the summer on some black and red rims.
The amount of money i've put into this car is easily three times the $1500 USD I paid for it. The list above doesn't even include exterior flash (Z3 fenders, altezza lights, pretty blue light for the dome) :)