Does exchange value have a foundation?

Market Value i read got a boost when Von Neumann amongst others took it 2 be a relative term definable by peoples choices of 1 thing over another - given a choice between things. Like my results network this runs in to problems if one attributes an actual quality 2 this difference. 1 may expect some one 2 prefer A over B and B over C but one cannot then assume they will then prefer C over A! An example of this occurs in my relationship with things. When home i use t internet and at t moment i use t library in town. Because i do this it is obvious to assume i value them and t argument would go tt i should pay 4 them. But i was thinking 2day tt had neither of them been created i wouldn't be using them and would be doing something else instead. In other words where a comparison cannot be made then no relative value can be assigned. One can only say i value there things because i use them. This does not assure tt i will use them in future or miss them if they suddenly cease 2 exist - tho human habit makes people return 2 what they know in favour of seeing things tt no longer exist as if they had never existed. But does this make things valuable? So in a free market where shopping is something people do anyway can we really use t actual exchange of goods as any evidence tt people value there things?