well you can buy a new p95d (blued) for under 400--generally around 350--anywhere you go. a kp95d should not be more than 400 new. and why a stainless slide would have rust i have no idea. i would say that if you buy it for that you are getting a decent deal. but if you talk them down to ~225 you are getting a good deal.
having said that--i love my ruger p95d. i had 2 problems with it. the first was that the leaf spring that keeps the mags in failed and i would drop mags if i didn't have a pinky underneath them. also the little retaining ring that holds the recoil springs on fell off. it still functioned perfectly but it was sometimes trouble keeping the springs from disappearing when i would strip it down. i called ruger and they sent me the parts for free. actually the sent me an entire new cam/spring assembly. and the guy offered to walk me through how to replace everything on the phone if i needed the help. i love their customer service.