Realistic Budget for Japan

There's been quite a few posts on Japan lately (it seems everyones going there!). I'm going in a few weeks and i was wondering what kind of budget most people would reccomend per person, per day? A friend told me a cup of coffee can cost $10 in Tokyo! I will (of course) be visiting several theme parks so I have to take this into account, and I am partial to the occasional extravagently posh meal :?

Forgive me if someones already answered this question somewhere

i took 50,000 yen when i went and that was for 17 days and i still had money left over of course i was staying with a japanese famly and was going to school there