Click send too soon... food and hotels are not expensive... you can find decent hotel for approximately US60 per person per night, and if you are willing to go one notch lower in quality, you can get away with around 45US$. Check out
JapanHotel.net Japanese Business Hotels, Ryokans, Minshukus, Guest Houses, Hot Springs and other accommodation they can offer you some advince
Transportation is what kills you, you can spend easily over a hundred dollars US if you are not careful with your transportation choices, Taxi cost a lot, unless you are splitting the cost with a big group. I wrote a starter guide here:
Lights, Camera, Action......
Small souvenir cost between 300円 750円 (key chains and small artifacts), while some more traditional ones cost up to 3000 or 10000円 (consider 100円 = 1 US or CDN)
Get yourself a JR pass (
http://www.japanrailpass.net/), you will be relying heavily on the Yamanote and Chuo line when you are in Japan, each ride (depending on distance) will cost you between 120円 to about 350円
Good luck, let me know if you have further questions, i will try my best to help