Let's say I have a buddy, Bill, and we go out for dinner every so often. He doesn't make as much as me, but he fights me for the bill every time. I end up paying less than he does most of the time.

I tell my wife, "You know what, it's not fair that Bill pays so much all the time. I should pay more."

My wife then says, "Your argument is confusing, and what's more, it's feel-good bullshit. You didn't give me a specific number on how many dollars you'd want to pay. Would you pay with a credit card? Traveler's Cheque? Based on total after tip or before?"

The supposition between reasonable people should be that I pay some reasonable amount more than I have been paying, but I don't go over the top and foot the entire bill. Is it fair to ask how much more I'd be paying? Of course, and the final justification of just how fair the arrangement is would depend on that number, as you've said. However, it's perfectly reasonable to say someone should be paying more, and have a discussion on that topic, without having to go deep into the specifics of how much more.