I care what AWS charges me; I don’t have the energy to care what their underlying cost structure and its constituent parts looks like.

As I said in my comment, their underlying cost structure has a direct relationship to the cost you incur (at least in the long run with semi efficient markets). There’s a reason why commodity markets tend to revert towards variable cost.

> There’s a reason why commodity markets tend to revert towards variable cost.

Is that some theory of economical model ?

Or is that a way of saying the final price of a product varies greatly because the commodity part with the product is only a small percentage of the TCO / BOM ?

Indeed; we shouldn't care about AWS power efficiency but we also shouldn't assume that it's bad just because we can't see it.