It will probably not be his last offense either. He's well off as you said, so his parents will probably bail him out of the situation to protect themselves from the embarassment their son has caused them.

One of my best friends was selling marijuana behind my back (i am STRONGLY opposed to it) and had he gotten locked up for it, I would not have helped him out because that would not teach anything. Him sitting in a cinderblock room for a while would give him time to think about how stupid he was for doing what he did. Your friend chose to take the risk, and he got caught whether it was his first time or his 300th time. I also find it humourous that his "first time" consisted of him having THAT much marijuana. Hopefully he will sit in jail for the alotted time and learn a lesson from it, because next time will be worse than this.