Go to Jessup.
Call ahead. Most of the space is professional and wholesale. But they have a few retail spots as well.
Best deal in town.
MARYLAND WHOLESALE SEAFOOD MARKET
7901-A Oceano Ave.
Jessup, MD 20794
The Maryland Wholesale Seafood Market opened in 1984 when the Baltimore Fish Market closed. The Market is the regional seafood distribution facility for the Mid-Atlantic and its twelve vendors form one of the largest operations supplying fresh seafood and shellfish to the East coast. Wholesalers market fresh seafood from the Chesapeake Bay and Atlantic waters, as well as exotic imports, to restaurants, grocers, and specialty stores.
The Market consists of over 112,000 square feet of packing, refrigeration and distribution space. It is open six days a week all year, closing occasionally on holidays. Several merchants also sell seafood products to the general public on a retail basis
Where are you located?
When my church did a large lobster dinner, we were buying enough (3 or 4 large boxes) to warrant wholesale treatment, and we got very good treatment from Profish in Northeast DC (202) 529-3003
You'll have to call ahead to arrange what you want, do without any hand-holding, travel to a seedy back street in a scary industrial part of Northeast at a shockingly early hour, and have some plastic tarps to keep any liquids from soaking your vehicle, but you won't beat the price, the freshness or the quality.