Some of it may be that owners have been turned off by Alex Robinson's arrogant rants, 'uneven' customer service and the fact that you need to loctite small parts in order to keep them from falling off the rifle. I think many of the 'range' only guys realized the AR-15 offered them a better and less expensive option, while many of the heavy-use bush hunters tried them and then went looking for something that didn't need to be babied quite as much. Others probably decided that the rifle's ergonomics weren't quite what they were looking for and decided to sell it and get something with a better balance suitable for carrying afield all day.
In all honesty, the XCR's I handled really were not worth the asking price. I could see picking one up if the price was around $1000-$1100, but not for double that. In that range, I'd much prefer to put extra cash with it and buy another Swiss Arms, Tavor or even a RFB.
The Swiss Arms is a known quantity and quality that holds its value, while the Tavor and RFB remain/are sufficiently rare that they too hold their resale value, at least for the current time. I doubt if current XCR sellers are going to be as lucky to recoup their original purchase price in the EE. However, stranger things have happened and all the more power to them if they do.
The XCR-M will probably prove to be a much better buy for anyone focused on an XCR. The larger caliber is more practical for a hunting rifle and makes it that much more versatile and in demand, as non-restricted .308Win semi-auto military-style rifles are much less common than their centerfire .22 cousins.