If you want to experience a delicious and cheap Japanese curry look no further than Matsuya.
Matsuya is vending machine gyudon and curry house. Simply select your menu item from the pictures on the vending machine, insert your money, take the printed ticket and hand it to the chef, then take a seat. In almost an instant your steaming hot and tasty meal will be delivered to your table.
A full meal including a main which might be gyudon or curry with rice, a drink, salad and miso soup will usually set you back somewhere between 500 and 1000 yen; an absolute bargain.
These restaurants are often very busy all through the day. Lunch times are often extremely busy when the usually all male clientele will often queue for a spot at the counter.
http://www.matsuyafoods.co.jp/english/