I have the same problem with Zeiss lenses as you have. Are their prices reflects “quality” 3 times more expensive as Nikkors. If they are 50% “better” I would buy one. However I never saw on internet that anyone say ZF are far ahead of Nikkors. Even 1.4/85 is rather far behind Nikkor 1.4/85D. I have some doubt even and with 1.4/50 that is better than Nikkor. My interest was Macro and recently I saw some test on Nikonians.org 3rd party lenses section. Nikkor 45P shows better “sharpness” at F2.8 than ZF Macro 50mm at 1.5 meter distance. However that test is done with dig. Camera so might be is not true to what I want to know.
Anyway as you are interested in Macro too my doubt is so great that it is (50 macro) any better than Nikkor 2.8/55 micro which I have and can say that is top class lens. The only I wish more is Leica bokeh and is the reason I still look around. If you can accept average bokeh you will be far more happy (print quality sake) with Nikkor 2.8/55 micro. I am just afraid to invest $1600cdn in ZF Macro just to test it. Actually I need for average distance (1-2 meter) and just sometimes for very close.
I just would like that someone say and show what is it better with ZF 2/50 macro over Nikkor 2.8/55 micro. What is it?
ZF 2/100 is full stop faster than Apo-Macro Elmarit 2.8/100 Leica. Also Leica is produced with much better glass than ZF and cost around 2 times more, but Leica does not claim so much as Zeiss does. What is true about ZF lenses I also would like to discover, but looks it is all big secret. Only resolution which photographers does not need. No one publish the truth with evidences. Always some talking around.