Thats...not quite a meant by high end. I mean stuff like a bespoke PCB so you can change all the switches out, an aluminum case... one of those $500+ custom jobs that /r/mechanicalkeyboards likes to drool over.
Full size are rarer and more expensive. There might be some other options.
Honestly the GMMK full size is pretty nice and you can pick whatever switch you want. It doesn't have a custom case like the one I linked above, but its aluminum and you can customize everything else. Some people have even dissassembled the case and painted it.
It's a very very deep rabbit hole.