Setting financial boundaries

How do you set financial boundaries with a friend when planning a trip together?

For context, I’m 25M and a huge traveler. I’ve been all over the world and on a budget because I enjoy it and get to see tons of awesome places. Hostels, backpacking, walking everywhere, overnight buses, public transit, etc. don’t bother me at all.

My buddy is the complete opposite, which is totally fine. Not everyone enjoys traveling that way and I don’t judge him for it.

He wants to do a week in France and Germany, stay in hotels right in the city center, take guided tours, and fly between cities (Paris → Frankfurt → Berlin). I’ve already been to both countries and told him that with those expectations we’re probably looking at 8,000–10,000$ for the trip. They’re expensive destinations and costs add up fast. Flights alone from California are about $700 if we book now.

The problem is that I don’t want either of us to be miserable. I’m willing to spend more than I normally would if I were solo because I value the experience of going with him. At the same time, I don’t want the budget to spiral completely out of control.

I’ve tried suggesting compromises. For example, taking a bus or train between cities instead of flying to save $, but his response was basically that it takes too long and we’d waste too much of our one week.

I told him I’d be interested in doing the trip together, but I’d really like to keep my total cost around 5,000. I’m struggling with how to set that boundary without sounding cheap or controlling.

Has anyone dealt with this before? How do you handle travel planning with one person on a budget and the other on a higher budget.