Wedding gifts: How do you give them?

Do you have a fixed amount you spend on wedding gifts for everyone? X amount for friends, and Y amount for family? Do you feel that your gift amount has to "pay" for the meal / party you get?

I've heard so many different methods about what people do and for whom. The subject is weighing heavily on my mind right now because I'm going to a wedding this weekend at a *vehry* chichi Manhattan location, black tie and all. Some friends feel that they have to buy a gift that would sort of "pay back" the value of their place setting, and are spending big bucks! (I mean, it wouldn't suprise me if this is about $300/person wedding.) I like this friend, but hey, I don't have that kind of scratch. Nevermind that Spouse is coming with me. That scratch x 2? Forget it!

Co-invitees who are no more related to the bride and groom than I am (that is, not at all related) are making fun of another friend who is thinking about spending just $100 or so on a gift: "How can he do that?! I would do that only if I *weren't* going to the wedding. How much is the couple spending on US?"

I hate thinking of it all as a tit-for-tat. It's not my fault that this couple has more money than I do and chooses to have their party at a lavish spot. And why, if I'm following this "pay for your plate" rule, would I spend more on a friend than I would on family members who have had their parties at, you know, the American Legion or whatever?

Help me figure out what to do. I have an amount in mind and I"m just going to spend what I'm comfortable with, right? Or is that cheap?