I didn't think you were putting down Poser, I just wanted to point out that there are all kinds of levels to the question. I think another way to look at it might be to say, "Is the work copyrightable?" In this case, the work (arrangement of pixels, if you will) is copyrightable as original work, even though the models are purchased.

I don't know if you use Poser or not, but I can assure that it takes more than 30 minutes to create a good image, even before you do the post work to it. I don't know what's typical, but I recall that my rather modest entry into the Halloween contest took about fifteen hours of work, not counting the rendering time when I went off to do other things. My image was a mix of pre-made figures and items I modeled myself, pre-made morphs and some I created myself with magnets, pre-made textures and some I painted myself, and my own lighting arrangements, as well as a certain amount of hand painting afterward.

Like I said, it's awfully hard to draw that line.