Economics has overdeveloped tools for reasoning based on price information in a "free" market of "rational" agents, and underdeveloped tools for actually valuing resources from first principles (because predicting the future, of a system involving agents, is really really hard). The former corresponds to your first axis ("how much you want it") and the latter to the second axis ("how much it costs the world to let you have it"). That's why, when facing any hard problem, the economics solution is to assume that markets will figure it out i.e. the two axis are equivalent, or that the first axis is the one we ought to work with, when making decisions (Further, whether the two should be conflated is actually a political decision, which is ignored in this sly exchange!)

The challenge is that real interactions are very different from a free market, and human agents are far from rational (for any operational meaning of rational that isn't tautological), unless in very narrow settings.

Economics doesn't have an answer to that, which is understandable, because it is a hard problem. The annoying things is when people pretend that there is nothing missing, and that everything is fine and dandy with economic metrics and tools. (EDIT: Economics is nowhere close to the physical sciences in its level of empirical rigor. Comments implicitly comparing economics to the sciences only serve as proofs illustrating my previous sentence.)