The same games and settings you would run using 2k Euro machine. No really, after some point you are literally throwing truckloads of money for very very small performance increase if that.
Honestly, I don't think there would be any difference performance-wise in games between let's say 3k Euro PC and 5k one, because what would those 2 extra thousand give really? SLI maybe? That's about it. CPU-wise I7-8700K is a top gaming choice and from there it's basically throwing more cores for little benefit in games (or even actually drawback because clocks drop).