It's not the quality of the lenses when choosing an f2.8 over an f3.5 it's the ability to work in lower light levels, that makes an f2.8 lens far more desirable. Simple supply & demand pushes the prices up for the f2.8's.
Both my TLR's have f3.5 lenses, sure I'd prefer an f2.8 lens on my Rolleiflex but as I was given the camera about 20 years ago I'm not complaining.
Sometimes strange things happen with second-hand prices and camera models, I've not really noticed with Rollei's but I have spotted that the budget Pentax Spotmatic 1000's & 500's often fetch more than the full spec Spotmatic II and F.
Ian |