I've been following the recent spate of high-end BT concertinas that have been listed on eBay.
In the week or so I've noticed a number of other concertinas, most likely unrestored, being offered for sale for what arguably seem like premium prices.
Here are some examples:
English Concertina Wheatstone Antique 30 key mahogany lachenal concertina with steel reeds Wheatstone 48 key treble English System Concertina made in April 1923
I suspect what's happening is, the vendors see top-end concertinas listed and think something along the lines of "grandad's old concertina looks just like that - it's old, it must be worth a fortune - better get it sold" without fully understanding concertina types and qualities, and the market.