This is kind of a complex question, but for those of you who live far from parents or In-Laws, who pays for your flights out to see them and their flights out to see you? Why? Are you happy with the arrangement or do you think it's unfair?

I'm obviously asking because I'm starting to get a little resentful about our situation and wondering what everyone else does. It's long and complicated so I won't write a novel trying to explain all the dynamics but basically somewhere along the way my MIL completely stopped paying for her flights out to see us even though she rarely visits and never offers to help us pay for flights out to see her. I'm wondering if we should start insisting that she pay her own way (which means she will probably never come visit) or at the very least ask her to help pay for our flights (4 tickets!).