Why? While I make no claim to being a market strategist I do have an opinion for what it it is worth. Cheaper solar has something to do with it, as does high priced diesel,as does the size of the market vs demand. Another factor is the Internet. Most people these days know their way around the internet well enough to price anything. They see something sell for $XYZ (or priced at $XYZ) and think, hey I have one of those myself. I am an active buyer of engines and engine cores for rebuilding and for my collection. Correspondence has taught me that there is one hell of a pile of both new and used Indian engines AND Dursley built CS engines in "unknown" condition both in this country and in Canada that can be purchased. Problem is the owners think they are worth 2-3,000 USD I have had some real doozies offered up for sale. Busted up, stuck, incomplete "used to run 15 years ago,,, da da da. Granted, A few will sell at those prices but not to me.
The reality of the slow speed diesel market as I see it is this;
I have watched at least a dozen Indian clones sell at auction over the last 4 years and have only seen one break $1000 and that was a brand new twin. I have never seen a CS single break $1600 at auction. Over the last 4 or so years I have purchased rebuilt and sold a dozen CS and Bamfords Z series singles. I stress that I do not sell used engines, only totally rebuilt ones and I stress TOTALLY. The CS singles run right at $3000, the Bamfords are $3500-4000. These engines are as new mechanically as I can make them. About half of my sales are to collectors, half are users. The market for my engines is steady, I have a backlog most of the time.
My market for used $2000 engines? Zero.