Fairlight-CMI

I have seen it mentioned here on this group about the IIx sale 
price. I was wondering why a series IIx is allways expected to list 
at 3500.00 and that is considered a fair price. I own 2 IIx's and 
(no they are not for sale), but as they get older and parts get more 
and more difficult to find I would think that that fact alone would 
drive a working machines price up. I would assume this to be true 
with series III machines as well. About a year ago I was thinking of 
selling one of my IIx's to a local buyer. I was asking 4000.00 at 
the time. The buyer told me the most he would pay is 3500.00. I was 
just wondering if there is something out there that states this is 
what is a fair IIx price. 

Kevin Kelley