Practical question on valuation of old systems

[Chuck Guzis]

Some of the collectors might be able to answer this one--or maybe 
not.  I'm just curious myself.

When one is dealing with 70's-era personal computers, does rarity 
play any part in the valuation?  

For example, would a wood-cased People's Computer Z80 box right out 
of Berkeley command significantly more than, say, an early Apple II 
or a Zorba?   (Not that I have any of these).

I've been browsing the ePay auctions and I can't seem to make heads 
nor tails about what sets the value of early personal computers.

Cheers,
Chuck