Vampire Bloodlines has been on sale at £3.74 previously which IMO is a bargain.
The official/full price of games on Steam is largely irrelevant unless they are new releases, because most people only buy older games when they are on offer anyway. Why single out Activision - plenty of other publishers have 'unrealistic' pricetags on their backcatalogue:
Bethesda:
Morrowind, over 10 years old, £12.99
Oblivion, 7? years old, £14.99
2k:
Bioshock, over 6 years old, £13.99
Rockstar:
GTA4, 5 years old, £19.99
...you get the idea, every publisher has high headline numbers on their older games on Steam.
To be fair, the Blizzard arm of Activision do seem to retain prices at high levels, I've been waiting ages for Starcraft 2 and Diablo 3 to drop under a tenner.