This is my first bargain post, so be gentle!
LocoRoco Midnight Carnival is usually £11.99 on PSN, and the Bui Bui expansion pack is £2.39. There is also a strategy guide for the game priced at £1.59, making a total of £15.97.
However, if you search for the Ultimate Pack on PSN, it includes all three of these items for only £4.79!
Metacritic score is only 73%, but for under a fiver it's well worth a punt imo :)