There are several factors, of course. Such as condition and desirability, also how badly the seller wants to part with it. Does it need any repairs or "tinkering". Consider, too that once P/W has exhausted the parts that are 800B/C, etc. specific, factory support will cease. $200 to $400. My opinion only.
Correct me if I'm wrong .I talked to PW as I have a C series machine I saw the writing on the website about parts be discontinued . Per PW alot of the new 800 + parts will work on these older machines . As i have found the heads to be the same to change gauges . I also asked PW what parts i need to keep on standby the answer was nothing. Now i would have purchased these item had they said i needed these items
I inquired with P/W about my old 800B (cira 1976). I had added all of the updates to this machine. P/W informed me that most of the 800+ parts would fit and would still be produced. However the one area that P/W said would be discontinued is the original 800B/C primer feed. So if you want to order backup parts it should be for the primer feed that fits at the bottom of the machine (not the tray or feed track).