Yes you can pay a lot more for sushi at Michelin multi-starred counters if you want to, but Kyubei offers excellent quality fish at somewhat more affordable prices, especially at lunchtime, in a much more relaxed setting. (Some of the chefs even speak a bit of English.) Kyubei were the inventors of gunkan-maki (the wrap-around technique for fish roe and similar sushi). Lunches start at Y4000 for a nigiri set menu, or Y8000 for omakase. Dinners from Y10,000, with a Y30,000 kaiseki sushi course that's quite a spectacle.
This book will introduce you to more than twenty of Japan's favorite specialty foods that are less well known abroad, along with a guide to the best places in Tokyo to try them and expert tips on what to order. From Bento.com.