Adorama has an used DA21mm Ltd (condition E) at $379:
Used Pentax SMCP-DA 21mm f/3.2 AL Wide Angle Auto Focus Limited Edition Lens - Black

A good price in my opinion...

[Mikesul]

This price is medium to high form what I have seen sell lately. Lots of asking prices higher than than but not selling. The lenses I have been watching have mainly sold below $350.

[luftfluss]

That does seem a tad high compared with last year. My DA21 from KEH last year was $329 in EXC+ condition.

But given that there are a number of poor copies floating around - I know from personal experience - I'd recommend buying from a store with a good return policy, rather than an individual. So perhaps paying a bit more is worth it.

[Mikesul]

That does seem a tad high compared with last year. My DA21 from KEH last year was $329 in EXC+ condition.

But given that there are a number of poor copies floating around - I know from personal experience - I'd recommend buying from a store with a good return policy, rather than an individual. So perhaps paying a bit more is worth it.

Luftfluss has a good point. It depends on how much risk one is willing to take. I have had excellent results buying from people on this forum and even Ebay. Ratings, pictures etc need to be examined very closely.