For example: I have a "cocktail" style pin-table which was made in limited numbers and an even more limited batch were sold in the UK. We are talking 4 or 5 currently in the UK out of 500 or so built. Considering the same machine in the US will fetch $1000 or more, one would presume they would attract a higher asking price? It seems not. When the owner of a well known UK pinball parts distributor queried about buying it for his own collection he said he could only offer me £300 max because that's "what they fetch on Ebay". I don't think the one he was referring to even sold, because it didn't reach the reserve, but this has effectively set the value of my machine to £300.
I've always felt more comfortable with the dedicated slot auctions like those hosted Jerry Chattenton.