[Jimfear]

It's been said before, it can be said again. Instead of the 31ltd you can choose any Pentax 28/3.5 or 35/3.5 incarnation, as far as I know they are all excellent. I own the K version of both lenses and although I would like the speed of the 31ltd I can't complain about the image quality.

For the other limiteds I don't have any personal experience in the range they are. But I guess the samyang 14/2.8 could be a replacement for the DA15, not really in the same weight class though.

[vanchaz2002]

an all Limited prime collection, what third-party manufacturer would comparable?

What do you mean limited prime? In FA series or DA?

If you mean FA, then you can get DA limited that are significant cheaper.

If you mean DA, then you may have some alternative auto focus FA/F to replace 70mm. You just need to find a cheaper copy of F/FA 50/1.7.

DA21 and DA40 have no cheaper Pentax autofocus alternatives. All good/fast FA/F ones that are wider than 25mm (DA 40 equivalent) are more expensive than DAs.

Fast Pentax manual ones in K and A are not cheaper to replace DA21 and DA 40. Half of them are much more expensive. K 15/18 are way beyond the range. K17 is fish eye and K20 is about the same price but hard to find. K28/2 is at least twice more expensive. K28/2.8 is not that great. K24/2.8 is the only reasonable one in K series. Also you can consider K24/3.5, cheaper but not always available.

No one is A lens wider than 24mm is cheaper than DAs.

For DA70, bunch of fast 50/1.4 is good alternatives.

[Laurentiu Cristofor]

It's been said before, it can be said again. Instead of the 31ltd you can choose any Pentax 28/3.5 or 35/3.5 incarnation, as far as I know they are all excellent.

Or you can just hold on to the kit lens as it covers well this focal range.