We believe that at the end of the build the final price will be about the same. While the frame and body costs are higher, A good bit of money can be saved with the cost of a donor car. A good usable VW Beetle donor will cost in the thousands, whereas a Cobalt wreck can be purchased for hundreds. If you do not have a donor VW then the cost of good parts purchased individually is even higher.
Our GTX dealer in Iowa is building a GTX for his personal use. He purchased a wrecked (hit in the rear) 2010 Cobalt for $750.00, it had factory aluminum wheels, and good tires. He spent $125.00 in gas and tolls to pick up the car. After removing everything he needed, including wheels and tires, he sold the remains to a local salvage yard for $250.00. That put his net cost at $625.00, for the engine, transmission, rear suspension & brakes, throttle & shift assemblies, radiator & fans, wheels and tires, wiring harness and computers. So at this point, he is even with or less than a VW build.