Who says you have to bring a gift. I have actually had people call me for wedding, baby shower or birthday party and say they couldn't come because they couldn't afford a gift. I have started using the old "No Gifts Please, Your Presence is Present Enough" quote on invitations just for that reason. (if people can bring a present then they usually do, trust me they will call and ask)

I say do what you can do. No One should ever make you feel bad about how much your gift is worth. If they do then maybe your the one who got the present.

Just a thought