Earlier quoted context omitted.
> In the upper class, oftentimes one person will pay for the check and it's awkward to object. That's how it's in my country for all classes, poor or rich. When friends go out, someone and pays for all the others (and someone might ask to chip in or pay themselves, but the first one doesn't take no for an answer). Next time you see each other, the other person can pay, but no one keeps any very specific tally ("I pai…
That only makes sense if you're consuming roughly the same amount. If you have people who don't drink alcohol in your group, or don't eat meat/seafood/poultry, that's easily 15% to 30% difference in cost. I try to make sure those aren't sharing in alcohol or meat don't end up paying for it. It wouldn't be a problem if the difference was $5, but nowadays, in many cities this ends up being $10 per drink and an extra $1…
In our culture's case, in general the amount each one ate doesn't matter -- whether one had steak and the other just a salad, the salad person can very well still go on and insist on paying for everybody else. Nobody would care about "a 15% to 30% difference in cost" (the person paying for everybody wont feel it's a burden, and the persons having their meal paid, wont feel like imposing).
It's not about achieving some perfect balance or fairness in any particular meal -- people genuinely want to treat others, and enjoy taking turns doing so.
It's only longer term one would care for patterns of behavior (the person who after so many meals with others never volunteers to pay etc).