What is the average gift you give at a bar mitzvah?

Chai, the hebrew letter equivalent of the number 18, means good luck, so this is a common gift. Especially since it is coming from a 13 year old, I think even $50 is completely unnessesary. At my bat mitzvah, 7 years ago, most of the checks from friends were for either $18 or double chai, $36; either of those would be perfect. Good Luck!