A record can be hot for a short time,if one is sat doing nothing in your box, and the price has gone up from 50 to 250,what you gonna do? Alot of theses type of sales are one-offs,one seller has one copy.
Take Lee Fields.After JM's auction (375),it was on here for 600 and sold.!!The price then fell to around 250,never again to reach that big price.
The prices are ultimately set by us with help from lists,auctions and whispers at niters .When you need a tune,you need a tune.Sense sometimes takes a back seat.