See Blue Fin on Chompster
Blue Fin in Porter Exchange is one of our favorite haunts for cheap sushi. They offer sets of 16 pieces (nigiri or rolls) for $18, 21 pieces for $24. Actually, I don't remember the exact prices, but the more you order, the closer the price gets to about $1 a piece. You can choose from most of the common sushi types - salmon, tuna, ikura, uni, octopus etc. without extra cost.
The quality is decent, but don't expect top grade fish. Do stay away from the uni too unless you are feeling particularly lucky. We've only had fresh uni there once. :p We typically stick to the nigiri too since it's more value for money =) ... as part of the 21 piece set, you can pick rolls too, but each roll (smaller and less fish) counts as 6 pieces!
I had the Squid Natto set on Friday night. It comes with rice, a side of squid and natto, salad, soup, tofu and shiu mai. Natto is this weird, sticky, stinky, fermented soy bean thing that I happen to love. Definitely not for the faint hearted. The Japanese mountain yam set is pretty yummy too. The texture is white and gooey but tastes execellent with some tuna, soy sauce and wasabi.
The squid natto set:
1815 Mass. Ave (Porter Sq. Exchange)
Cambridge, MA 02140
4 Stars for cheaper prices. This is a favorite haunt of ours so yes we'll be back! I also recommend stopping in at Kotobukiya (japanese grocer) to stock up on Japanese snacks like Pocky! Oga's in Natick however is our restaurant of choice for quality sushi.