A friend decided to spring for a half-dozen lobsters last weekend, so I convinced him to save about $30 and go with me to the fish distribution center, located down by the stadiums on Packer Ave. near Front Street. I usually go to Samuels & Son (on Lawrence). While these places really are wholesalers, they do "tolerate" walk-up retail sales. And, it's pretty much the nearest you can get to "fresh" in the City, since all fish is flown/trucked there first for distribution to restaurants and mongers (caveat for Morimoto, I'm sure).
It's a bit intimidating at first. You park in front of the loading docks, walk up the stairs and just ask a white-coated expediter for what you want. There are no signs, no prices listed -- availability depends on what they have. Price is determined by the going market rates. Once you place your order, you're given a ticket, which you take inside to the office and have your order processed and the final price tallied. Back to the expediters, who package your order. Then back to the office to pay.
We got six 2-lb lobsters at $8.50/lb. I saw them going for $12/lb later that afternoon in the Reading Terminal. You might get a comparable deal in the Asian markets, but I'm always a little wary about those tank fish. I asked about the bags of littlenecks they were loading onto a truck: 200 for $50. Softshells? Barely in season, and they were sold out, so prices are iffy, but one worker quoted me a "flat" (one dozen) for $25-27.
When I make salmon consomme, I'll go there for salmon carcasses. Last time, they led me to the fish cleaning room, where 4 or 5 workers were filetting enormous salmon for delivery to the fish markets -- it was a pretty amazing sight, what with water flying everywhere, electric scalers humming. They told me they just toss the carcasses anyway, so how many did I want? Out came a contractor bag full of enough carcasses to make mass quantities of soup. No charge.
I believe you can call in an order ahead of time, which would allow you to confirm the price of your product in advance. Samuels & Son Seafood Co., near the corner of Packer and Lawrence,(215) 336-7810.