Who says Tokyo is expensive? There are plenty of places where you can have a hearty meal for just 500 yen (one meal, one 500 yen coin). It won't be a glamorous affair, but it will do the job and won't burn a hole through your wallet.
The absolute king of cheap meals is Yoshinoya, which has been in business since 1899. Their specialty is a bowl of rice topped with thinly sliced beef and onions (gyudon in Japanese). A large serving will only set you back 480 yen.
Yoshinoya has inspired plenty of competitors to dethrone it from its pole position in cheap meals. Sukiya and Matsuya are going for the same combination of cheap beef bowls and curry rice, Katsuya and Nakau serve fried pork cutlets, while Go Go Curry and CoCo Ichi specialize in curry (you might have to add a couple of extra coins at CoCo Ichi).
The other restaurant that took Tokyo by surprise is Tenya with its 500 yen tempura and rice bowls (tendon). For only an extra one hundred yen, you can eat a superb tempura lunch at Tempura Imoya, not far from the Imperial gardens.
If in Shibuya, be sure to check out a Sunnypages users' favorite, Shanghai Shokudo, where you can have an incredibly large and tasty Chinese meal for exactly 500 yen. If a couple more coins are not an issue, the nearby Kanichahan offers fried crab rice and crab soup for just over one coin--amazing! In Harajuku, our users have fallen in love with Gyoza Rou, where the servings cost under 300 yen, and is a perfect spot for late-night beers and food. Check also the nearby Otoya, where the set meals come very cheap and change with the seasons to offer the best.
If burgers is what you want, it is hard to argue with the 100 yen burgers at McDonalds and its clone competitors. But, you might want to splurge a bit more and pay just under one coin for a burger at MOS Burger or Freshness Burger--two Japanese chains that use organic in-gredients and that are known for quality. Suehiro in Ginza also offers a complete burger lunch for one coin. On the healthy side of the equation, there's Soup Stock, where the sets come just above one coin, and feature healthy soups with a bowl of sesame rice.
Finally, there's always a lunch box (bento). Every convenience store carries them, there's specialized stores like Origin Bento, and if you walk around a business area like Akasaka at lunch time, you'll find plenty of restaurants that pack their food to go for just one coin.
Who said you need to save for a month to dine out in Tokyo?