Well, first, I didn't see any rude answers. If your FMIL knew about this large number and what the cost would be, that's a fairly significant detail to leave out. This is huge for a rehearsal dinner, and most were probably thinking of an event less than half that size. And your wording implies you're trying to force her to have an event she can't afford, since she's the one who should be arranging it. I'm still confused as to why she needs so much help. Is she asking you for ideas? And if she can afford $50/person, why are you having trouble finding a place that's affordable? There's nothing wrong with a fixed price menu offering two options, but I do think any alcohol made available should be free to the guests. Can you work with the restaurant and only serve, say, house wine by the glass? Something like that would work fine, and there's no need for champagne or even anything else at a rehearsal dinner.