Hmmm, the "beginning guitar" thing sounds like a very plausible explanation for part of it, particularly given what types of guitars are on sale.
That said, I am also seeing Taylor's "main line" 300+ series guits within a few years old on sale with regularity, but not so with the older, say, "pre-Andy" guits (more or less, not exclusively "Andy" models, of course). All anecdotal observations, of course, and just wondering aloud. It's likely a combination of a bunch of things, of course. Interesting thoughts, though, to be sure!
Edward