I'd be curious what they were wanting the money for personally. They can't possibly expect everyone to give just cash. I personally don't understand why holidays and weddings are always about what the persons get. Shouldn't it be a celebration of two people coming together not some charity ball???? Just a thought. But at any rate if it's money they're asking for, no matter how much you give if they're truly your friends they will be appreciative. Especially be conscientious of what you write in the card, that'll last much longer than any money you could possibly give and is much more meaningful. $25 would be appropriate, but no matter what you can give it'll all add up with everyone else's gifts. I just hope they don't open their "presents" at the reception. That can be VERY embarrassing to everyone.

Some other ideas would be to have something engraved with their names and wedding date, that's something that they would not have and mean a lot.