Recently got a 200 f/2 for $4100 in near perfect condition thats about a year old. A MKII 400 f/2.8 for $7500 that was used ONCE.
I feel bad about the 400 f/2.8 mkII as I bought it from a friend who had no clue what he was doing. He bought a 1Dx, 400 f/2.8 mkII, 70-200 f/2.8 mkII, 50 f/1.2, 1.4 and 2x TC MKIII, full RSS setup: Versa 3, BH-55, Lplate, PG-02 Full gimbal and about another $2100 in accessories. To this day I have no clue why he did it... but I guess its nice to have money.