As an example, one couple I know has the husband making significantly more. The husband contributes 80% of their earnings so that they both can live in a nice apartment in the nice part of town. The wife contributes 50% of her income and keeps 50% so that she has a similar amount of personal spending. They discussed this and were fine with it.

I think after making this one decision, they no longer have to have discussions each time someone spends more than x amount for a completely joint account