Why are there no good AF 50mm lenses available for Nikon?

It appears no, there are no AF options other than the Nikon and Sigma offerings.

But again the Leica lenses are not AF either. So the problem you have is not that there are no "Leica quality" 50mm AF lenses available for a Nikon camera. The problem is that there are no "Leica quality" 50mm AF lenses available. Period.

It appears that only Leica is able to make "Leica quality" 50mm lenses. They are all manual focus, and they cannot be adopted to Nikon DSLRs.

Just as Nikon cannot or do not want to make a "Leica quality" 50mm AF lens at any price, Leica cannot or do not want to make a "Nikon quality" camera at any price.

It appears whatever you do, if you want a 50mm lens, you will end up with a compromise. If you go with a Leica system your results may restricted by a less than optimal camera and the lack of AF. Or if you go with Nikon your results may be restricted by a less than optimal 50mm lens shot wide open.

The Leica compromise will cost you about $8,000 more.

You just have to set your own priorities and make a decision accordingly. I cannot offer any help with that other than to say that from my own personal perpective the Nikon AF-S 50/f1.4G lens is just fine.

Go hire one and try it out and see what you think.

Good luck.

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Cheers,
Peter Jonas