This has also been on my list for a long time. I have a couple that are close, but I have never had a 75.
If you see a low or even apparently reasonable price, but in "original condition", it almost certainly needs a rebuild, and you need to factor that in to the true cost of ownership.
If it is rebuilt by a competent person, it will almost certainly be at a higher cost, and possibly worth it..
This is one of those collector traps where "original condition" sounds like a good thing, but even a cosmetically perfect rifle that old (the cherished "safe queen") has seals that have turned into a doughnut of hard parmesan cheese.
There are people with the time and skills to DIY such a rebuild, but I am not one of them.
They are lovely rifles, and my ancient but resealed Diana 65 (Winnie 333) can play pretty competently with a FWB300. Since the '75 is the improved version, yeah, I want one, and you do too. Good luck and if you get one, please post pics!