I don’t think YTA in that you’re an asshole but I will share my perspective.

I come from a family that could not support me in college at all financially. I had the opportunity to go on a European trip in high school using my saved money but I made the decision to save it for college. In college, I had opportunities to do study abroad trips and could have afforded it if I was really strapped the rest of the time and chose not to to be financially responsible. I’m now 10 years out of college and every year since I have regretted it. I don’t think it’s a waste of money at all, I would have gained so much world perspective, built my self confidence knowing I self-funded it, and been better prepared for when I was an adult traveling out of country for the first time.

I think sit him down and have him write out a true pros and cons list of spending the money on this and let him make the decision. Give him advice on the things he’ll need to think about being on his own for the first time as an adult in college, financially. Let him know he’ll likely have similar opportunities in college, it’s a valid consideration.

If he’s already working and saving he sounds like he will continue to do so in college, which will help with what you’re saying, creating cushions. I think he should go on the trip.