I'll admit it: I'm guilty of buying film off of ebay because I could not afford certain types any other way.

I wonder how much of a negative impact ebay sales of expired stock have on sales of fresh stock (contributing to decreased sales).

I see most of the cheap, expired film on ebay with bids on it when I look. So people are buying it. Honestly, the fact that there is so much on ebay expired, tells me that there is more being manufactured than can be sold before it expires. In the early 2000s, it was more due to people switching to digital, but surely by now, most who were going to switch to digital, have switched and have either used up or already sold off their film.