i think you also need to add downsizing by some aging collectors, who may not want to leave that much for others to deal with ( i have told my kids to pay attention because their inheritance, pitiful as it is - is in double barrels and old books)
personally- I think its a leap to say the changing hands of high grade shotguns is a sign of tough times. lots of them offered with no buyers accepting maybe, but not simply the fact that they are offered and most often find new homes
I also expect lots of folks limit themselves to how many - or their safe limits them- i saw one yesterday I really liked- when I got home I told my wife about it and said I just have to decide if I like it enough to send something else down the road to get it
have not decided yet- but I did look at the seller's info again this morning - just to be sure I did not lose it