Every seller is a "For Sale by Owner." Every buyer is a "do it yourselfer." It is simply a matter of how much of the work in a real estate transaction is contracted to a real estate professional. From none to the entire transaction. Or in industry speak, from the stereotypical FSBO for a seller to a "full service" listing.
Property and homes are commodities, pure and simple. High demand and low supply drives prices higher and the asset becomes more liquid (easier to sell). Low demand and high supply drive prices lower and assets become less liquid (harder to sell). Market value is ultimately determined by what a buyer is willing to pay and a seller willing to take. I hear the following statements from consumers: Well, I can't sell for less than my tax assessment! My home is worth at least my appraised value! My neighbor said... My Mom told me... The one down the street sold for...and my home is better... Zillow says...