i was just at a chump car this weekend in CA and alot, ALOT of the cars looked substantially more than $500. that said, the racing was still good, and if you weren't really looking for a win it was pretty fun. fastest times were the two exhibition class spec miata's on race tires. lots o' grip.
if its any consolation, i would value an alfetta at $500 because the chance of wining is low! ;-)) there's a number of car's out there that are lemon's legal.
cruise the San Francisco craiglist list and you'll see cheap alfa's occasionally.