Poisson, you're missing the point: if I buy and shoot only x-ray film, the quality of the art I create is irrelevant. The fact is, I'd be using (and therefore buying) the x-ray film as a direct stand-in for Tri-X or whatever other photographic film. Rare is it that one would buy significant quantities of both the cheaper substitute and the expensive name brand option.

You buy a pair of nice running shoes and pair of cheap knock-off running shoes, you're always going to run in the better pair. Some might say they would use the cheap pair for muddy running or what-have-you, but if you prefer the better/spendier shoes, you'll use those as much as you can convince yourself to.