Furcafe sold his Nokton to me, and I am very happy with it. Even wide open is is sharp. I haven't tested it against Leica 50's, because I don't have one. I do have an Olympus 50mm f1.4 Zuiko, the latest one with the serial number over 1,100,000 that is reputed to be the best OM system 50/1.4 version, and I have an AF-Nikkor 50mm f1.4. The Nokton is a lot sharper wide open than the AF-Nikkor, and is very comparable to the Olympus (which is a far better lens than the Nikon in my opinion after using both for many years).
The Nokton costs $360 new. I got mine far cheaper buying it used (Thanks again, to furcafe for the good deal he gave me). Even if i'd paid full price by buying it new, it would be WAY less than a Leica lens (even if the Leica was used). I can't see that the Leica lens can be much better, and even if it is, I doubt you get your money's worth.
Here's a Nokton shot, wide open. I focused on the closest eye.
Here's one stopped down, I think at f11. The thistles in the background are very detailed if you see the photo blown up.