Is there another name for marginal luxury? My coworkers and I were talking about the concept of voluntarily paying more than you need to for something. As an example, I can buy a locally grown organic apple from the farmers market for \$3 or a conventional one from the grocery store for \$0.50. We can say that the \$0.50 apple is a basic level of consumption- society agrees that I deserve that apple as a human right (or, we can expand the argument to a basic level of consumption including shelter, food, etc). Since I paid \$3 instead of \$0.50, I paid an extra $2.50 for the luxury if it being a special kind of apple I prefer.

We called this amount "marginal luxury". Does economics have a proper name for it? Is there a reliable source of how much of an economy, say the US, is marginal luxury?
The closest I can think of is Stone-Geary utility/preferences, where consumption is assumed to provide utility only above a specific level (the $\gamma_i$ parameter in the link), which is usually designated as the "subsistence level".

As for how much an economy is above this subsistence threshold, a way to roughly assess this is to calculate what would Total Income be if all people were at the poverty-line-income (each country determines its own poverty line). Then subtract this from the actual Total Income. What is left can be thought of as what the OP is looking for.

But calling it "luxury", implies that any consumption above the level guaranteeing mere survival is a luxury. Is it?