Sigma 300mm

[SJTstudios]

Popular 3rd party 300mm
Sigma 300mm 2.8-$3,399
Sigma 120-300 2.8 os-$3,199

Why is this???

The 120-300 is newer, is a zoom, so it should be more expensive, has os, and apparently faster af.

Why is the prime more expensive?

[pwp]

Interesting question. Here's a review of the still current 120-300, an update has been announced and will ship when Sigma decides to get on with it.
http://www.the-digital-picture.com/Reviews/Sigma-120-300mm-f-2.8-EX-DG-OS-HSM-Lens-Review.aspx

And 300 f/2.8 reviews:
http://slrgear.com/reviews/showproduct.php/product/227/cat/all
http://www.lenstip.com/index.php?test=obiektywu&test_ob=221
http://www.fredmiranda.com/reviews/showproduct.php?product=128

I don't think the fixed 300 has had a refresh in a while, and I believe still lacks OS. I'd hang out for the updated 120-300 zoom.

-PW

[Mt Spokane Photography]

One reason might be all the OS failures on the Sigma 120-300.  It seems to be carrying on the Sigma penchant for unreliable OS.  Everyone is hoping that the newer version beefs up some of the weak points.  I will not be wanting to buy one just to see.