Actually, I'd have to respectfully disagree with that. All other things being equal a 5:1 price differential does generally equate to better quality, but the circumstances here are slightly different; one is an exotic piece of glass while the 50/1.8 is a very simple optical design. The 50/1.8 for example is also frequently believed to be better optically than the 50/1.4 which is a reverse of the, more expensive = better, guide.
I also wouldn't say the 16mm is one of Nikon's standout performers generally speaking; it's good especially considering its age, but for example all things being equal I'd rather have the 10.5mm than the 16mm, and both of those are priced more or less the same.
I advise you to give up on trying to compare 2 such totally different lenses. In both pictures I can see that the image is sharp where it should be sharp, namely on the focal plane. Other than that, differences in aperture and field of view cause too many differences for a valid comparison.
Might as well take a Kia Cerrato and a Ferrari F1 car and say "compare".