The Kaplan online course is new. Kaplan just switched to a new curriculum (fyi, which is actually mainly like the old stuff with a few minor changes like a few new strategies and quizzes). Most folks here will tell you that the subject test questions are the most valuable component of the curriculum...and you get those with the online course. I'm not sure if you get the three tests (diagostic, midterm, and final), but I imagine you do. What you don't get is the live instructor...a lot of folks don't think the live instruction is that good, but I think it depends on who your instructor is. But at any rate, personally, I think the $800 is worth it for the questions alone. Oh, you also get powerpoint type presentations on the lesson material. They used to have an online video series, but they took that away because of the new curriculum. I'm told they will have the online video series eventually, but that's not the case right now.
Don't consider it an online course...it won't be one. It'll be more as if you get access to the test questions for a period of time (3 months I think).