Not sure of the cost....maybe $15.00. Others will have a definite answer for you.
Wanted to say that you can easily walk to the Dolphin from the Epcot International Gateway and from the Disney Studios. From either it's like a 10-15 minute walk. You can also take the Friendship boats that travel from the Epcot IG to the Disney Studios througout the day. They stop along the route at the Yacht/Beach Clubs, Boardwalk, and Swan/Dolphin. If you plan on being in Epcot World Showcase or the Studios the day you want to eat at the Dolphin you can get there easily from either park.