The difference between value and price, recognized by traders, institutions, market makers, etc., attempting to make a buck on the market, has spawned individual theories for determining the value of equities, options, commodities, etc., as opposed to their price (such theories are sometimes known as the trader's "edge") and methodologies for not losing your shirt (risk management). Both are needed.
@flengyel No, actually! Made me think that value=discounted expected price (ofc very different from the Marxist notion)
Wasn't that boring?