Monster Sushi is good, but if you want good sushi that is inexpensive, and you like real crab in your rolls, try Westside Sushi, 717 9th Avenue near 49th St. See link below for the menu.
Ninth Ave. between 43rd & 53rd has some great restaurants and bakeries, btw. A good/quick escape from the hectic theater area.
http://menupages.com/restaurantdetails.asp?areaid=0&restaurantid=3888&neighborhoodid=9&cuisineid=62&home=Y