as sarnie said that's how a scam works.
i actually got caught out many moons ago, with western union, think it was on something cheap, but had no guarantte like credit card or payal.
however it could be possible price if needed a quick sale.
i would think current market, if needed a trade in price offer would probably be similar, so it's a more realistic price.
it's the ones which should be say £10-15k advertising it at £5k or something which are definate scams