[Brightcolours]

I'm sure that the 21mm f/2.4 is an awesome performer but fact remains that the pricing is a bit surreal.

If true that's 50% more than Sony/Nikon are asking for their 20mm f/1.8 - thus even faster/wider lenses.

You may argue with the build quality - maybe - but this is still a steep difference.

I suppose that Pentax is banking on their reputation in JP. Just from hearsay, they seem to have a more Leica-like image there. It's probably their main market nowadays.
Of course, if it's working out for them, they should go for it.

You're comparing with the wrong lens - the Zeiss Loxia 21mm f/2.8 has about the same MSRP.

I could argue about many things, although the optical qualities of this new lens are yet to be discovered (however, we do get some good hints). I could argue about the Sony and Nikon Z relying on software corrections, for example, and being mirrorless lenses thus much easier to make. And yes, the build of the D FA 21mm is on another level. I could argue about mechanically connected focus rings, too.
Did Sony and Nikon put a similar amount of effort into their lenses' rendering as Pentax did? It's too bad the others don't do "development stories" the same manner as Pentax, so we're not told what they had in mind when designing a lens.

And then - as you said - if it's working out for them, they should go for it.

Ho hum.

Yeah, you are comparing wrong as the much cheaper (almost 1/3rd of the price Sony 20mm f1.8) is wider, faster and much, much cheaper!

Did Sony make a lens that renders beautifully? (yes...) 
Did Sony make a lens that relies on software corrections? (no...)
Did Sony make a much simpler mirrorless lens? (no... Almost the same weight, more elements (14 vs 11), and I doubt this Toki... I mean Pentax (sorry for the typo) reaches the same quality).

For sure we should only compare it to the very overpriced and slower Zeiss lens.

Also, just about the same can be said about the Nikkor 20mm f1.8 that can be said of the Sony... Does not rely on distortion, renders beautifully, is much cheaper yet has 14 elements. 

The difference appears to be that they spent less money on the nonsense sales copy than Pentax does.