The thing is, the 400/2.8 is a money maker, as there really isn’t a lens out there that renders like it.
Is the rendering between a 58/0.95 and 50/1.2 really different enough to support the difference in cost? Personally, I don’t think so.
I find it a bit weird Nikon prioritized this lens instead of doing an AF 50mm 1.2 S lens first, but I can see some practical applications for things like video, high end portraiture and top level landscape work. Also I know there's a subset of well-heeled photographers who can easily purchase this lens. Nikon might even just do a limited production run and the value of the lens might skyrocket afterwards, so who knows! Saying that, I'm still pretty happy with Nikon 50mm 1.2 AIS which I got for a good price!