I assume you meant to say that those who want it more will pay more for it (otherwise, well, yes? people who don't want a good will not pay for it by definition, ones who do want it will pay something, so they will pay more).
What I find hard to reason about in this area is comparing how much _different people_ want something. I can tell how (in a world of perfectly honest and omniscient people who will answer all questions) to tell whether one person wants X more than Y ("what would you do if you could pick one of them only?"). Do you have a candidate definition (or something that points in the direction of one) for comparisons of wants between different people?