If you've booked an Airbnb with kitchen, you can purchase some items back to cook. You can get the fishmongers to prepare the seafood for you like slice the fish into sashimi slices, open the clams.
We purchased some large cockles at 5kwon for about 1kg(?) at the street market. Shellfish along the streets are fairly cheap.
Inside the building, there are live seafood. Very little crab options but lots of humongous lobsters (could be due to season?) as compared to noryanjin in Seoul. We were quoted 50kwon for a 5kg lobster. Didn't purchase cos we felt was too expensive. But you can pick the seafood and they'll get a restaurant to cook then upstairs.
Overall I prefer Noryanjin over Jagalchi. But each region has their recommended cooking techniques.