I only collect cheap RFs now.
For info on expensive RFs, like Leica M6, ask other members here.
Contax stopped making RFs a long time ago.
They only got autofocus G1 and G2 recently. Now it seems Contax not carrying on with Kyocera.
Some RFs (most not made anymore):
Nikon RFs (made first in 1948, sold later in USA in 1950s)
recent remake for collectors. very expensive. $2000+ British Pounds.
Contax folding bellows RFs
Canon GL III QL, 7s (F0.95 lens),
Ricoh ZF, Ricoh ME, 500G,
Minolta ALS, 7S2, 7S, 9, himatic E, himatic F, himatic G, CLE
Yashica Electro 35 GSN, GTN, MG, GX, Lnyx (F1.4) etc....
Olympus 35 RC, RD, SP-N, XA
Leica CL, G3, M2, 3, 4, 5, 6, 7 (6 or 7 still being made) costly
Alpa sw12 (new and very expensive)
Fuji GS, GW 6x9,
Kodak folding Retinas
Petri 7S
Konica auto S2
Rollei XF35 ( some MADE IN SINGAPORE)
Shanghai 205
Zorki 2C
FED
Voigtlander Bessa 2 (Apo Lanthar lens)
Modern Voigtlander Bessa RFs made in Japan
Zeiss Ikon - modern ones soon available
Vito range of RFs from Voigtlander (before 1980s/90s)
Balda and Solida - postwar Germany
Linhof technika. costly
maybe Speed Graphic too
HongChi - Maoist era China-Leica M copy. Now very expensive since rich PRC Chinese collect.
Gandolfi - eccentric Italian modern medium or large format RF. solidly made. costly.
and many others......