[Human-Cabbage]

This conflates use-value and exchange-value. Water to someone dying of thirst has extremely high use-value, while a diamond would in that same moment have nearly no use-value, except for the fact that, as a commodity, the diamond has an exchange-value, and so can be sold to help acquire a source of water.

[js8]

In a sane world we would just give the poor guy some water and let him keep his precious diamond. And in the sane world, the guy would donate the precious diamond to a museum so that everyone could enjoy its beauty.

What are you describing happens if you follow the mathematical rules of your models too much and ignore the real world.