If you are buying or selling a 3 bedroom, 2 bathroom house, you feel satisfied with your settlement price if the value is roughly what similar homes have sold for in the neighbourhood in recent times. If you are opening a hairdressing business, you will price your services on the basis of what others in the profession are charging.
The prices of Banks beer, Carib and Heineken are not identical, but they are comparable. The ruling prices that we observe in daily commerce cannot be explained by established economic theory, even though theory may be employed to rationalize them after the fact.