My .02 cents for what it will cause. I own a large collection of swivel knives. I do have to admit that my SK-3's are my most used and favorite ones next to my Craft Japan. I also agree to what was also mentioned earlier, you buy what you can afford. If your pocket does not allow something heavy like a Pro-series (which hasn't been mentioned), SK-3 or Ol'Smoothie than there are some more affordable products out there. My Craft Japan 11mm knife was a gift, but at $29.99 (minus a blade) it works twice as good as some of my $50 knifes.
The swivel knife is (in my opinion) the most important tool in my leathercraft hobby. It took me a long time to learn this lesson, I believe the hard way. One of the artists that I follow and listen to has written about having a sharp swivel knife or using a sharp swivel knife. I now know this to be so true.
If you are serious about your craft, I would carefully consider your knife options. Now, with this said, I can say that I have taught myself (with the help from other to include Paul at LW) how to sharpen my knifes and how to use rouge. I would seriously recommend that you learn how to do this.
I bit you good luck in your search!