>One results in the loss forever of the treasure; the other at least preserves them.
you paint an unfair picture.
you fail to mention that, in the case of this argument at least, preserving the artifact by means of foreign intervention may very well result in the starvation of the would-be local thieves.
many would argue that the loss of any human life is greater than the loss of all the world's artifacts.
It isn't really that unfounded a concept.
A well studied and documented artifact has only a specific amount of practical importance, aside from some sort of cultural significance. A human life has an unknown future, be it good or evil -- and unlimited (human) possibility if given the opportunities.
It's a fairly simple value proposition when simplified unreasonably this way : "Do you let another human die for the sake of storing an already studied artifact in a location where the object is safer?"