I have this lens- picked up for $20 at a camera show. I picked up three Leica mount lenses, all 90mm, for $60. Gave away the 90/4 Elmar after doing a CLA on it. I have a couple of them.
The Sun: compares with a coated post-war 9cm F4 Elmar.
If prices are up on the Sun lens, it is because of being rare compared to the Elmar. Look for a lost-war Coated Elmar. The pre-war uncoated lenses are extremely difficult to clean haze from inner optics. The post-war coated lens in chrome is the one to get.