At those same yard sales, you could usually pick up 8 tracks for a buck or two. CDs had not yet been invented, but the 8 track was already dying in favor of cassettes, and the quantity of 8 tracks available at yard sales steadily increased while the price dropped. I actually bought (at a yard sale) a portable 8 track player (probably for $2 or so), because I realized it was possible to negotiate the price on the tapes down to essentially nothing (a quarter or 50c for a bag of them, type of thing), if it was after noon on a Sunday, or a single day Saturday and after about 11 a.m.
If you're cheap and/or broke, stocking up as a format is dying is a fantastic way to develop an enormous collection for very little, and if you have the time to go to a lot of places, you can even get just about whatever you might want that wasn't created after the format peaked. Which is a bit of a trick if you think about it.
The consuming herd has some interesting dynamics. When a format is new and expensive, it isn't possible to buy -- at any price -- used copies. People have only just bought them and aren't done with them yet. As the format grows, the early adopters will start to unload stuff they don't care for to make room for new things. As a replacement format appears on the horizon, early adopters might dump an entire collection as they switch to a new format, but there will still be people actively consuming the old format for a while -- you can get into a situation with three or more formats (LPs, 8 tracks, cassettes, then LPs, cassettes, CDs, etc.) live at once. But at some point, no one new is starting to buy the older format(s) and a lot of people are switching and, thus, a lot of people are clearing out the old and looking to convert it into money. It must be worth something, right? They spent all that money, and for most of that time, used was a good fraction of new, so someone wants to buy my old stuff, right?
At this point, libraries usually start putting up desperate signs saying "no cassettes" or "no VHS" and used bookstores say "no encyclopedias" or whatever. Places like Half Price Books just put together a recycle policy and dumpster the stuff, giving you a lump sum for the stuff they want and offering you to take the rest off your hands for free.
The internet and, in particular, sites like Amazon, Half.com, eBay, paperback swap sites and so forth put the Annie's Book Stops of the world Right Out of Business -- that's a general increase in the liquidity of goods as shops moved to a lower-transaction (lower rent/more customer visibility) universe and turnover increased. But eBooks post-kindle have been a New Format problem, so I've been wondering when the new format dynamics come into play: when do we hit the point in the adoption cycle where there is more supply of used books than demand? Obviously, we've always been at that point for books that some delusional publisher thought would be bestsellers but instead was remaindered. But I'm waiting for a more general form of the problem, and I believed it would be more visible to me when libraries started getting really picky about book donations, mostly because I didn't think I'd see it on the used-books-for-sale side.
But I'm wondering.
Should I believe this?
"The estate clear-out people trashed most of the books in my parent's house. Not even Good Will takes unpopular types of books." Good Will is getting picky?
ETA: I doubt it.
Not sure what's going on, but so far, this still looks like the increasing-liquidity of show-your-warez-to-everyone-online, rather than a format change.