TravelIf you plan to do a lot of travelling in Japan then it is worth getting the Japan Rail Pass, which allows unlimited travel on almost all JR trains, including the shinkansen (excluding the Nozomi superexpress). This pass can only be purchased outside of Japan and will save you travel money in Japan.
In Tokyo, most of the main sights and hot spots can be visited via the JR Train Line (Yamanote loop line) with a one-day JR train pass for 730 yen (about USD$9). You can also look at regional pass like the JR Kanto Area Pass.
AccommodationPossibly the biggest expense will be accommodation, but there are quite a few cheaper options including:
Capsule Hotels – which range in price from about USD$40-$50 a night with access to baths and sauna.
Minshuku Japanese style guesthouses – are great simple accommodation ranging from about USD$37.
Business Hotels – a great compromise with prices around USD$70 for a single room and USD$100 for a double. I recommend the Toyoko Inn hotel chain located all over Japan as they include free breakfast, TV, and internet connection in your room.
If you are thinking of being in Japan for an extended stay, you might want to check out guesthouses offering discount for language lessons such as Share Style: http://www.share-style.net/
FoodPrices at regular Japanese restaurants are usually USD$8-$15 a meal, but food can cost you as little as USD$5-8 a meal if you eat at budget Japanese restaurants like Yoshinoya, Sukiya, and CoCo Ichiban Curry House. Look for lunch set specials, which are great value and cost as little as USD$7-8. Some fast food restaurants have them even cheaper at around USD$5.
AttractionsMany attractions in Japan are free including temples, shrines and gardens. The more famous attractions will charge an entrance fee but this is usually as little as 500 yen about USD$6.
I would say about USD$80-100 per day is possible done on a budget. Start saving and plan a trip to Japan on a budget in 2012.