Bill, 
  
I'm thinking more along the lines that a scrap yard owner would buy an old junker for $75 then sell the right front fender for $50, the rear bumper for $35, the hood for $40, etc.  Much the way this seller seems to buy a model kit for, maybe $75, and sells a hood scoop for $16, a bumper for $10, etc. 
  
Yes, the cost for a used part vs. a new part is much lower.  The point I wanted to make is, buying the parts to build an entire car or model kit would cost many times what the car or kit would cost if purchased as a whole.  Regardless of whether the parts are new or used. 
  
This is something scrap yards have been doing for the last century or so. 
  
David G.