Ordinarily, a meal of sushi is a costly indulgence. The rock-bottom alternative is a kaiten-zushi, where sushi is literally served assembly-line style: chefs inside the circular counter place a constant supply of dishes on the revolving belt with plates color-coded for price; just choose whatever takes your fancy as the sushi parades by. A cheerful, bustling example of this genre is Heiroku-zushi; it's all about the fresh fish here (and clearly not about decor).
When you're done, the server counts up your plates and calculates your bill. Expect ¥126 for staples like tuna and squid to ¥367 for delicacies like eel and salmon roe.
5–8–5 Jingu-mae, Tokyo, 150-0001, Japan