Disclaimer: not related to this original thread, just a general comment.
Im not really convinced it is 'supply and demand' as much as 'inadvertent market manipulation'.
Put something up for valuation and it almost becomes like an old style auction game where someone shouts £1000, the next shouts £1200, everyone just going higher and higher as if they win a prize by saying it is the most sought after cab ever. Until someone comes along and gives a lower price and gets shot down for heresy - 'cab prices can only go up and up and up!'
And even if the cab sits there unsold, or never even gets put up because it didn't reach the sellers expectation, it is still seen as its 'value' because, hey, that's what people valued it at, and then the next cab up for valuation gets valued higher because the original one was and that shows the market is booming...
perhaps the only people who should comment on 'valuation' threads are those who are actually in the market for the item, at least that way they are putting the money where their mouth is. I know that is close to an 'auction/sales' post but ultimately, what is the point of someone saying something is worth £2000 if they wouldn't pay that for it
'How much is this cab worth?'
"£2000"
'OK, gimme £2000 for it'
"No thanks, im not spending that amount on it. I was just saying its worth £2000 to someone else, who I don't know, and of whom I have no idea of their wants or financial situation. But its worth £2000 to them!"