[Brightcolours]

My understanding is that the 58mm f1.4 deals with correcting coma and apparently it is an expensive thing to do.

Correcting coma is not that expensive. And they did not correct it all that well either, by the way (the old lens does a better job? And the Sigma does a better job also). The lens does not contain a lot of glass (see its weight, and number of elements).

Of course, you will also note that it's a 58mm lens and not 50mm. Nikon didn't add an extra 8mm just for the hell of it.

They added it for old times sake (linking it to the famous Nikkor Noct 58mm f1.2). Back when the 58mm f1.2 was designed it was easier to make a 58mm than a 50mm due to the flange distance. When the old 58mm f1.2 was introduced, it had a reason to be more expensive, because back then aspherical lens elements were expensive to produce. But the art of lens design and fabrication has evolved a lot, and nowadays even consumer standard zooms like my EF 28-135mm f3.5-5.6 IS USM have  aspherical elements.

 

The Sigma has 13 elements. Special glass: 3 SLD elements and 1 aspherical element. Weight: 815 grams.

The Nikon has 9 elements. Special glass: 2 aspherical elements. Weight: 385 grams.

The Zeiss has 12 elements. Special glass: 6 low dispersion elements, 1 aspherical element. Weight: 970 grams.

(For fun and illustration) Canon EF 28-135mm f3.5-5.6 IS USM has 16 elements. Special glass: 1 aspherical element. Weight: 549 grams.

 

So, it is not the amount of glass that would justify the high price of the Nikkor.Nor is it sharpness of the design. It is not the coma performance either. 

 

Coma Sigma:



Coma Nikkor:



 

They already have more 50mm varieties than I have fingers.

Did you have an accident? Nikon at the moment has 3 current 50mm lenses, if we count the 58mm also. AF-S 50mm f1.8, AF-S 50mm f1.4, AF-S 58mm f1.4. If we count the on special order still available old MF designs (55mm f2.8 micro, 50mm f1.4), just 5. 

 

To be very frank, there is no reason for the high price of the Nikkor, other than marketing (linking it to the 58mm f1.2). On the performance side, it does one thing well, and that is bokeh rendering. The Sigma seems to do that well also. For the rest, the Nikkor has very high LoCA, is very soft wide open and in the borders, does not ooze build quality. If it has been f1.2 like its forebear, the high price could be justified.