Yashicamat 124g 6x6 tlr @ about $200. Just bought one (unfortunately had to return due to overlapping frames) but I can see from the roll I shot that the lens is very very good, matching up to my Rolleiflexes. Handles great,bright easy to focus screen. Makes
the sound of a coffee grinder when u wind on the film.
Rolleiflex MX-EVS 3.5 about $500. Lens seems to match up to my 2.8 Rolleiflex. Incredible jewel like comstruction but kinda dim focus screen.
Mamiya 645 Pro series system SLR. Under $500 w lens. Excellent results, easy to use, big heavy, not very fun. A tool.
Fuji GW690 series - can be found under $600. Texas Leica. Awesome lenses and results. 6x9 image can be cropped down to pretty much any other mf format w zero loss of quality. Solid, sturdy but not really fun to use if that matters.
Lomo LC-A 120. Quirky but can give great results. Does not feel built to last.
Anyway, the above are mf cameras that I have used under $600