I think it's worth it. I went through a school to get it via online at http://www.cbcwebcollege.com and have found it to be a great way to learn. I like how I can "talk" to it and the feedback it provides me. Through this online program, it only comes out to $15 a month for access to all languages (including Japanese) and all levels. Not bad, especially if you want to see what the first level is like.
I really do like the style of learning RosettaStone represents. It's, as they say, "painless." But, no doubt, it is extremely helpful to know people who are native speakers with whom you can practice. That's fun. And makes the whole process worth it.

Sounds a lot like livemocha.com, which is generally free. (except for some of the premium videos etc)

Luckily I only paid 25 dollars for Rosetta Stone because my cousin works there, because it sucks.

I think its a good supplement to other methods, but as a primary method for learning, I agree, not worth it. One thing it definitely wont help you with is learning hirigana or katakana.

But 500 dollars for supplemental?