The diversity of valuations and their volatility pose problems for a market
place, but the market-place problem can partly be solved by letting individuals
decide what they are prepared to trade for what, and then using some sort of
average rating across different individuals as the value of something
purchasable or tradeable. (However, "average" makes sense only if there is some
set of numerical measures to be averaged. Otherwise we can at most have pareto
orderings.)