I've found some terrific bargains on 20-25 ct shrimp at Jon's Markets. $4.99-$6.99 a pound at times.
Nevertheless, while almost all shrimp come to you frozen, do you know about brining to bring them back to their succulent, fresh state? If not, check this out. By the way don't try this with pre-shelled shrimp. You'll puff up and die.
To rehydrate 5lb blocks of UNSHELLED frozen shrimp, drop the frozen block into a gallon of 70 degree F water in which you've melted 3 cups of kosher salt. (To facilitate melting the salt, start with 2 cups of boiling water, then add cold until you reach temperature)
Let the shrimp sit until they've defrosted (45 minutes to 2 hours) and rinse well. Cook however you want. These will be some of the best shrimp you've had. Trust me. Would I lie to you?