As of right now D&D Insider is $5 a month (if you buy a 12 month subscription) for only Dungeon and Dragon magazines as well as the D&D Compendium and some online content. Once they get the other stuff up and running, they'll increase the price (who knows how much, but they have mentioned it will go up).
Right now, D&D Insider isn't actually up and running. I'd hold off and see how the virtual tabletop turns out. It might be neat, it might not.