About 10 to 15 years ago, someone did a survey of what it would cost to build a Mustang by buying the parts separately over the counter. The cost was astronomical! I think it was figured, you could buy three new ones from a dealer for the same cost. Today it would even be worse.
If someone had a donor car with all the parts, 15Gs is not that bad for a new body. I think a new MGB body is around 10,000 now and not near what the Mustang would be worth if done professionally. PJ