We saw a feeding frenzy late last year, and really nothing since then. M15s are so few and far between that it's hard to predict what individual sales will do -- steady supply and demand (and rational buyers) don't predict one keyboard going at $800, another a couple weeks later going at double that, and a New In Box (which has happened maybe twice in the last four years?) going at... about the same price a couple weeks later.
Shame about this one, really, he's going to scare off sellers, and after my refurb came back basically unimproved, I need another one -- but with the last one going for about half what this seller wants, I'll be holding out for, well, somewhat less, and with less uncertainty as to its condition.