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?
I think it does, but not as much as in some other collecting hobbies.
It would appear that nostalgia pays a big part in it too. At least in the
UK, Sinclkir ZX80s and MK14s sell for ridiculously high prices
(considering that particularly the former sold in quite large quantities,
and neither are interesting or well-designed machines), whereas some much
rarer machines get much lower bids on E-bay (there was a Tiger there
recently, it sold, IIRC, for about \pounds 30, and that is a pretty rare
machine).
-tony