Roughly 1-5 years ago, EBay consistently carried ~80,000 - 100,000 items in the Cycling section of the website, more in the springtime and less in autumn.
Twelve months ago, I think, Ebay began running promotions, including free insertion fees, etc., for people who sell in this part of the web site. At first the number of items jumped to 130,000 and imho, prices dropped a little and many items went unsold, including my own white O-rings for old Campagnolo brake sets.
Recently the number of items has been hovering above 200,000 (right now it's at 267,000!) which to me is simply remarkable!
- Don Gillies
San Diego, CA, USA