I think if people are trying to recoup some of their expenses, perhaps they should have looked into a cheaper option rather than expect others to pay for their place in the wedding. Your good friends could be living hand to mouth for all anybody knows. Personally I would rather have my friends there and give me nothing than feel obliged to give me something.
I do give gifts at weddings, baby showers etc but I give what I think what they will like. I have no idea how much it costs them to seat DP and I and if they think I am giving them something to the value of a few hundred dollars because they chose expensive food they've got another thing coming.
i am so, so grateful that my friends are not materialistic in the least. It's all rather gross.