Best I can find elsewhere is around £15. This is one of the E-Bay selected deal of the days with free delivery, currently 'more than 10' listed as available.
Quote from Zavvi.com:
It's incredible - it's huge - it's... the Pythons choosing their own favourite bits. At long last we find out which of the hundreds of sketches made it into their own Personal Best selections. All the classics are in here - the Lumberjack Song, Nudge Nudge, Upper-Class Twit of the Year and of course, the Dead Parrot. What's refreshing from these guys who, let's face it, have egos to contend with, is that they have even chosen sketches they don't appear in - but they just love to watch. With hilarious new introductions and links from the surviving Pythons, and a touching and insightful tribute to Graham Chapman from the rest of the team, this is the very best of Monty Python.