It's easy to say bad things about the GRE. It sucks to put in time and effort studying when you have homework to do, a job to finish, articles to write, etc. I feel your pain. But in the end, either you take the GRE or you apply only to schools that don't require GRE scores. As far as preparing for the GRE on the cheap is concerned, I would give you the following tips:
1. Buy used GRE study materials at Amazon, a local used book store, or other source. I've never been a Kaplan fan, but The Princeton Review is decent.
2. Take practice tests, especially the ones offered as software on the GRE website (with free registration).
3. You may well do worse on the practice tests than you do on the actual GRE, so don't get discouraged if your scores are a little lower than you'd like.
4. Just take the GRE. After you have done it once, the mystery will be over. Many people do better with a retake.
5. If you must get extra help to study, look into GRE prep programs offered by your school (which will be cheaper than Kaplan/ Princeton Review) or a tutor.