Are you talking about the later Bronica leaf shutter lenses or the early Bronica lenses for focal plane shutter cameras? I sold my 150mm Bronica Zenza lens on Ebay and only got $75.00 for it. The 75mm Nikkors went for even less. I've seen 50mm lenses go pretty cheap. I did sell my 40mm lens for $400-$500 but they are rare as hen's teeth and it went to a collector. The later Bronica leaf shutter lenses do bring more money.
If you had that 150 on auction with no or low reserve, than it is always a gamble with final price directly related to that moment of interest and from what kind of crowd. If you had it for BIN at 100-120, it was rather a sell if in great condition. But US market is vastly different from say Europe where Bronicas are on a different (low/scarce) supply level and prices are 30-50% higher. But similar difference applies to most photographic gear.
I think Japan is what represents "proper" market value for those trying to figure where the asking price stands in the "value" department. Then it is a matter of applying it correctly (i..e not forgetting customs, so for US delivery there is no customs so it is a WYSIWYG with delivery times 1-2 weeks, for EU is a near sure thing there will be, barring some lucky day in the office, and it is no chump change and around a month to see it). I once received a Bronica EC prism straight with no customs, but so far anything that weighs a pound or more seems to get noticed where you hope it won't. So for those in EU, if a lens sells easily in Japan for $100 and same in EU for $150, while the latter is still somewhat above your FINAL price, it may still be a surer option and much faster delivery.
For S/EC lenses, the 40 has been mentioned as much above the rest in price point, but also the Carl Zeiss Jena 80 / 2.8 is very rare, and the Nikkor H.C. 75 runs much above P & PC versions. Long focal lengths are actually on cheaper end (still higher than mainstream ones). All of it to keep in perspective when looking for a package as suddenly a lens alone may be worth more than asking price with rest a pure free stuff.