This is actually a replica of a famous 1963 Ed Roth creation that was later destroyed. Fortunately, before it was demolished, model company Revell, made a plastic model kit of Mysterion, preserving the design for posterity. Bachman commissioned this detailed recreation of the original.
Roth didn't make money building custom cars. He made money from selling t-shirts and other stuff emblazoned with his famous cartoon character Rat Fink, who was sort of like Mickey Mouse gone horribly bad. He also licensed his car designs to model and toy companies like Revell and Mattel's Hot Wheels.
An association with actor McQueen can multiply the value of a machine.