Regarding the value of an 88-note push-up player, if enough people
were clamoring for 65/88-note push-up players, and the supply of such
devices was insufficient, it seems to me the player rebuilding shops
would be fabricating new ones, either from scratch or by modifying
existing internal player actions whose pianos were defunct.  Yet, to
my knowledge, this isn't happening, at least on a widespread basis.

The price paid for any product is based on two things: the amount
of people who want the product, and how scarce (or available) it is.
The easiest way to find out how much someone is willing to pay for
something is to auction it off.  If two or more folks _really_ want it,
the price will go up.  If not -- well, you get the idea.

Bryan Cather