All fair points, but I don't think the company minds that much. His average price is low especially for 1st class, but they do have a small number of cheap tick

All fair points, but I don't think the company minds that much. His average price is low especially for 1st class, but they do have a small number of cheap tickets you can get if you book fast enough or there isn't much demand. I once booked an 8-hour international 1st class ride for 35 euros. The full price was something like 250. There is for sure a threshold where it would be too many people, but I don't think they'd mind a few more people dropped 8k on this. First class is not that full and 8k is 8k. On a personal note, I like trains, but not that much. One downside is that it's not guaranteed that he spends all his time in one train. It can be a bit of a distraction to have to switch trains. And also a bit tiring. Although since he I guess rides without a real destination he can just pick a train that goes across Germany, something like Hamburg - Freiburg.