The more important thing is that HE thinks that he's underpaid. It's clearly something that he's put quite a lot of thought into. I think that ultimately he's looking for a push, or some confidence boost, to approach his boss. So OP, my advice is this: look for a new job. You don't have to get a new job, but you can look. There's really no downside to it. Perhaps after a month you'll realize "damn, I can't find anything without taking a pay cut" and your problem is solved. OR, you'll find a company that loves and wants you for more money. Then you have ammunition (and confidence) to approach your boss.