Bare Shells for Race Cars - Value?

[mitchVR6]

Don't know if I"m in the right section for this. Moderators, feel free to move this over.

Does anyone know what the value of a shell is? I mean nothing, left on the car but a few body panels. Anything missing would be replaced with carbon / plastic anyway. particularly interested in:

993, 968, 944, 964 cars. I've been looking for prices and shells for sale and can't find anything anywhere.

Do people even buy/sell these things, or do they start with a more complete car as a base? We're talking race cars or maybe a street-rod for certain applications.