I took the Princeton Review course starting last July before I took the October LSAT, and couldn't have been happier with the course. I agree that it's a lot of money, and if you really do want to just study on your own - go for it! However, the structure of going to class every other day or so and having a set amount of work to do per class was a real help to me. I was lucky perhaps and had an excellent teacher. Hearing explanations and having the visualization of being taught on a marker board really reinforced the concepts from the book (that I wouldn't have gotten if studying on my own.) I think the class was worth the money just for the simulated tests on Saturday mornings as well. You can take all the practice tests you want at home, but there's something about waking up on a Saturday and going to a test that's run by a proctor.
Hope this helps! Best of luck!