I'm not sure to fully get the meaning of prices. If I understand well, there are two drivers of it :
The theory of demand and supply and thus prices are driven partly by the utility that agents get from it.
Production costs : On the long-run, prices look to converge towards something like the minimal cost of their production due to the fact that the supply side innovates enough to reach this (that's my interpretation). So on the long run prices of things tend to decrease.
But then, is there something such as the price reflecting the actual utility that consumers get from it ? Indeed, some goods are really cheap because there is a strong competition on it but nevertheless, they give their consumer a big utility (coffee for instance). Given the competition, even if the disposal to pay of consumers is more than 2€, they pay it 2€ (because no supplier could raise its price withou losing all the market). Therefore, we could have something like : all the goods that are produced at their marginal cost are underrated, have an underrated value and the true disposal to pay of people for it is higher. There's probably a flaw in my argumentation but I don't see it. Does anyone have an idea ?