You simply can't make money building PT cars and selling them. The labor and parts always exceeds the cars value. The uneducated always see the outside and don't consider what these cars actually cost.
I'm trying to sell my 1978 Camaro, Highly modded LS engine, Modded TKO, Moser rear, Hotchkis suspension etc..etc. Basically everything short of a new frame and a 4 link. I would say with parts and labor over the years, easy exceeds $25K with me doing most of the work. I have been asking $18K and someone offered me $8K stating "its just a 78 Camaro" they are not worth much.
I can yank the engine the transmission out right now and get close to $8K for it. The uneducated doesn't see a $10K drivetrain, a $2000 rear end, $2000 suspension, $1500 FI fuel tank, and the $1500 new interior. Your buying the parts and basically getting a free car! I really think that's how most people see these cars and that's what makes them tough to sell at reasonable prices.
Try finding a 11 sec Camaro that gets 20mpg with an interior and handles the corner for $8K