[Funny]

You are probably generalizing too much. What about those of us who have access to cheap parts? Junk yards? Family members/friends that are dumping their cars?

A junk run often time nets you with a part that you can't easily find, like a gear for a transmission, or a $100 tranny. These types of modifications are also partly for the enjoyment of besting others. Competition drives a lot of hypermilers.

So you have made a blanket statement, though it does have some truths in it because cost over time ratio is important, but it depends on the mod, and the sources.