I bought this set (originally it was 6 nigiri, ate one before taking picture) at Red’s Best Fish Market, in Boston Public Market at Haymarket for $17.95 ($3 a piece). They sell at the stand at Public Market as well Fish Pier besides, also grocery retail sashimi cuts (as/if what sea produces particular day). That particular day they had not much.
I found however same day (unfortunately no picture, per one per post Reddit rules – sorry) great selection at Maruichi Japanese Food & Deli at Coolidge Corner. Had slightly bigger than meat on picture cut of Chutoro for $12. Besides got myself: Blufin Otoro, Sockeye, really fat cut of other Salmon, Fresh Snapper, Yellowtail Hamachi (Pacific predator, not to be confused with Yellowtail flat fish from New England), Skipjack soared Bonito (really liked that one), some Roe, sauces, seasonings etc etc.
Along sister store across the street they have quite good grocery selection, cosmetics, some kitchen/sushi/sashimi-ware, teas, sake and wine plus bar.
Lady at register (probably owner) was extra polite/helpful/sweet as only Japanese can be. Love the place, and love beyond decent selection of Sashimi cuts.
by Kowalski_boston