If I could sidetrack on this thread: I have trouble losing the Rubber Eyecup on the 645D. They simply pop off very easily when wearing a coat, and arm rubs against it. I have replaced several times, and even Superglue the last one on. Lost it too. Adorama and BH both out of stock, i assume due to everyone else losing theirs too. Any tips on how to lock them down permanently?
As for topic, I have 75 and 45 in both MF and AF, and the 35MF and 55MF -- all of them are stellar, to me. And most of them averaged around $200 for great condition, at KEH, for the MF models. Amazingly affordable. I love the camera, except for the vastly underpowered writing engine. I hit the buffer very often.
If you wear glasses, you could always superglue one of the eyecups to your right eyeglass lens.
P.S. If you don't wear glasses I would disregard this suggestion.