Agreed that context is extremely important. Income is an imperfect measure of buying power, since prices vary significantly based on geography, but it is still a measure, and in the context of globally traded commodities such as energy or fertilizer it is quite important. The price of oil or fertilizer is likely very similar (if not more expensive) in Cambodia compared to a place like the US.

Well, $10 K/yr is only fortune in Cambodia because only few people live quality life and many people have to make compromises and sacrifices.

Whenever we analyze the such case, we must consider whole group. Nobody would live in city if the quality life is poor compared other place like rural area. Yes, there are few exceptions like people like to spend money over extravagance stuff. But they represent minority.

I would say Income does indicate a measure of real wealth or wellbeing.