333Jeff,
The short answer is yes, the overall double rifle market has been in decline year over year for maybe the last 8 years. A "fairly low" price is ambiguous….if it is priced to current market, it will sell.
That is unless the rifle is a fairly sought after "name" maker in top condition or something like a .577 NE.

Even a very nice boxlock NE from Brit makers does not command a break even price for someone that bought at the peak.

You can see this on your mentioned websites from various sellers as you named having rifles list for months or years and no sale. They bought in fairly high and now can't tolerate taking a loss. Guess they are holding out for a major market comeback.

You can look at Gunbroker, Guns International, and auction results and see what the current averages are running.

This having been said; how about some pictures of your Greener for us to drool over?

- Mike