"If there were more demand from an expanded pool of players for expensive instruments their price would come down."

Let me enlighten you Conrad (Not much hope I know!)
Here in the UK, there are 2 fine makers of quality concertinas. Steve Dickinson (Wheatstone) and Colin Dipper.
I visited Steve a few weeks ago, and while I was there, he had plenty of calls about new instruments from people willing and able to pay the £5000-6000 per instrument..(thats a bit of a guess, but was too scared to ask exactly what they cost!)
He was turning them down....why?
He is a one man business, he's turning 60 in January, and quite naturally would like to retire in about 5 years. If he were to take on all the requests for new instruments, he'd still be make him as he passed 100. Not to mention the repairs to existing instruments for gigging musicians.
I'm sure Colin Dipper is in the same situation.
So, as usual your statement is meaningless drivel. The demand is huge, and the supply is severely limited. Add that to the fact that every part of the concertinas are made by hand.
Steve told me that in a good year he might make 8 new concertinas. More likely 5 (what with all the maintenance work on old boxes).
So, with luck he might make another 25 Concertinas before he hangs up his tools, and I think they have already been ordered.

Quality instruments don't grow on trees Conrad. Massed produced junk does.