Just got off the phone with Pentax Service Dept. My DA*50-135 repair cost is $253.
When I had shipped it to them for evaluation, I had included a letter eloquently describing the problem (defective auto-focus), as well as detailing my history of Pentax product loyalty, and my disappointment with the quality control record of these "top-of-the-line" DA* zooms (my 16-50 had to be replaced, as well).
It made no difference- the lens was a bit less than two months beyond the warranty period; so, as far as Pentax is concerned, it's out of warranty, period.
I knew there was a problem, -before- the warranty expired, but I failed to fully investigate / diagnose it at the time. I guess I have no one to blame but myself for not addressing it when I could have. I'm biting the bullet 'cause I like this lens, but I'm still pi$$ed. So if any of you are experiencing problems with your DA*50-135 auto-focus, don't delay! Procrastination can be costly.
Paul