Unfortunately the developer has gone the way of a lot of the big name developers, where they release the game in an unfinished form then release a series of DLC's that add extra functionality to the game. This game in particular has had nine seperate DLC's since it was released earlier this year. The total cost of these is almost as much as the base game:
Sid Meier’s Civilization® V: Babylon (Nebuchadnezzar II) - £2.99
Civilization V: Cradle of Civilization - Mediterranean - £1.99
Civilization V: Cradle of Civilization - Asia - £1.99
Civilization V: Cradle of Civilization - Americas - £1.99
Civilization V: Cradle of Civilization - Mesopotamia - £1.99
Double Civilization and Scenario Pack: Spain and Inca - £4.49
Civilization and Scenario Pack: Polynesia - £2.99
Civilization and Scenario Pack: Denmark - The Vikings - £2.99
Civilization V: Explorer’s Map Pack - £2.99
Total cost of the DLC's £24.41, though you can purchase these in bundles that save you a few pounds/dollars
You do get one of the DLC's included in the Deluxe version, but the full price, which is £10 more than the standard edition that gives you the sound track, and a behind the scenes look at the game being made; hardly worth an extra £10 IMO, (though in the sale this equates to £3.40). The additional DLC you get with the deluxe version costs £2.99, so you're basically getting the behind the scenes and the sound track for £0.41 (while it's on sale) :)