repharim, we’ve already suggested your approach (you want an expensive wedding, you pay the difference for our guests), and it was rejected.
When we first met his parents, we asked how they wanted to split wedding costs. They said either 50-50 or according to number of guests on each side. Assuming they’ll live up to the latter, we’re now thinking that we’ll just invite a lot fewer people for the meal, and ask others just to come for the chuppah or the dancing. This makes me sad — we’d like to invite a lot of out-of-town guests and you can’t invite an out-of-towner just for the chuppah or dancing.