[MMM]

I would budget

$1000.00 for the flight
$200.00 a night for lodging
$20.00 a day for lunch and snacks
$30.00 a day for dinner
(if you just stay in Tokyo) $25.00 a day for train travel
$100.00 a day for cool stuff you want to buy
$40.00 a day for entrance fees to museums, or amusement parks