I think it's an interesting question too, but the question as its presented here seems to imply that cheaper options are somehow more morally correct than more expensive options, and I'm not sure that's always the case.
Take travel. Your carbon footprint may be higher if you fly off to foreign destinations three times a year than it would be if you camped in the country you live in, but there's a lot to be said for supporting other less well off countries with your tourism. Tourism is something that whole countries rely on to avoid mass unemployment in many cases, and these countries often don't have a welfare state for their people to rely on. So which is better - having a smaller carbon footprint, or supporting real families that wouldn't have any income if it weren't for tourists?
Take education. It's a fact that there aren't enough state school places for every child in the country. I'm lucky enough to live in the catchment of a great comprehensive school that people move into the area to get a place at. If I could afford private school, is my money better spent supporting the PTA of the state school, or is it better spent by allowing another child whose parents couldn't afford private school the chance to still go to a great school. There's no point pretending that all schools are equal, they are not, and they are not going to be any time soon no matter where my imaginary money goes. So here and now, which option gives me the moral high ground?
I could go on with other examples related to healthcare, buying luxury clothes etc, but you get the point.
You could find a principle that's worth sticking to no matter what your bank balance is.