From Mousesavers.com
"Pleasure Island allows guests to walk through during evening operations without purchasing admission. Anyone can enjoy Pleasure Island shops, restaurants, West End Stage entertainment and the nightly midnight "New Year's Eve" fireworks display at no charge.
However, admission is required for entry into any of the Pleasure Island nightclubs. (Also, you must be 18 or older to enter BET Soundstage, Mannequins or Motion.) There are now two forms of admission:
The Multi-Club Ticket gives you the opportunity to "club hop" all night for one admission fee.
The Single-Club Ticket provides one night's admission to one club at Pleasure Island. Choose from BET Soundstage, 8TRAX, Mannequins, Motion or Rock 'n' Roll Beach Club. This ticket may not be used for admission to Adventurer's Club or Comedy Warehouse. You can only purchase the Single-Club Ticket at Pleasure Island or Downtown Disney Guest Services.
For most people, the Multi-Club Tickets are by far the best deal, particularly since they give you admission to the not-to-be-missed Adventurer's Club. I suspect Single-Club Tickets will primarily appeal to locals who just want to go out dancing one night with friends."
Prices are:
Pleasure Island
Multi-Club Ticket - $22.32
Provides one night's admission to all clubs at Pleasure Island.
Single-Club Ticket - $10.60
Provides one night's admission to one club at Pleasure Island. Choose from BET Soundstage, 8TRAX, Mannequins, Motion or Rock 'n' Roll Beach Club. This ticket may not be used for admission to The Adventurer's Club or Comedy Warehouse. You can only purchase the Single-Club Ticket at Pleasure Island or Downtown Disney Guest Services.
All of this was on Mousesavers.com, you should check it out cause there are also tips on getting discounted tickets for PI too!