Costco ink refills are limited to certain printer models. When I asked at Costco about refills for my Canon Pro-100 I was told that they don't do them.
Welcome from Pennsylvania from a former K-100D, K-x, K-50 (died) and now K5IIs owner. I don't shoot wildlife so can't help you on that front. Always pleased to see another Pentax shooter!
If you're interested in Pentax do check out Pentax forums.com. Great reviews of all Pentax cameras (new and discontinued) as well as reviews by owners of the cameras. Honest answers to questions. Based on what I've read I would not get a K-30 or K-50 due to the above-mentioned quality issue, aperture block failure. If you buy an extended warranty you'd be covered. My K-50 died in a fall and while I loved the camera, i chose a used K-5IIs again based on what I read.