What is a bargain for sea mammal called?

There isn't a specific term for a bargain specifically related to sea mammals.

However, the term "bargain" itself is often used when referring to a good deal on any product, including animals. So, you could say something like:

* "That was a bargain for a sea lion pup!"

* "I got a great bargain on a whale watching tour."

If you're specifically looking for a term relating to the price of sea mammals, it's best to use the standard terms like "price," "cost," or "deal."