Personally, I don't put Confirmation in the same category as a graduation, and yes, I am a Catholic and have also taught the Confirmation class for quite a few years. IMO, being confirmed doesn't really require the same amount of work that graduating does. It should, but it doesn't, that's just the way it is.
That being said, yes, I would give a gift. I don't think I'd give $50 for a neighbor's child, unless we were very, very good friends. I'm thinking more along the lines of $25, but that's just me.
OP, give what you feel comfortable giving. No more and no less. If the newly confirmed really learned anything during their preparation, they will be appreciative of any gift you give.