well a Superformance finished goes for $40k
and a version of the Lotus 7 (like the Caterham and Donkervoort that is US built) called the S1 for $23k
Both have no engine or Transmission though like most kit cars so you have alot of freedom on that part.
And here are the Factory five cars minus the construction and drivetrain
http://www.factoryfive.com/table/ffrkits/ffrkits.html