What we consider valuable might vary with the culture. Consider the following Old Babylonian letter coming from what is now Iraq (about 1800-1600 B.C.):
Speak to Belshunu: Thus says Shamash-hazir.
May Shamash keep you in good health! I write to you time and again and you do not pay attention to my words. They are wasting wood and dung, so that you (must) be very alert. With respect to the wood I will treat you like an enemy of Marduk! Let the door of the staircase be sealed. Do not give one single piece of wood, apart from the one . . . that you give each time as a funerary offering. Take care of the matter of the wine, and if there is barley in the hand of the gardener, receive it from him. If not, have him brought in and confine him to the house.
(M. Stol, Letters from Yale [Leiden: E. J. Brill, 1981], 15-17.)
For us, it is easy to envision wood as a valuable resource, over which careful stewardship was expected. It is harder to envision dung as a valuable resource to be watched and warded, but even it was not wasted in the ancient world. It had its uses: fertilizer, fuel, filler in pottery, and so on. Sometimes what ancient people valued is by us counted but dross and refuse.