Well it is if you are in Europe. If you try the European currency beta option, next to my account on the top right, it says Bio-Shock is £13.99. Leaving the US currency on it is $54.99. $19.99 translates to £13.99 including VAT. Whether this is a bug or not I do not know, but you may want to take advantage of it while it lasts.
Sweet, definitely going to check this out when I get off work . . . and then, after I’ve gone to my next job and gotten off from there, and had some sleep, and been to work again.
Expect my reply sometime in the 2008 time-frame!
Couldn’t British users purchase the game “as a gift” for somebody else, and transfer it to whomever they wished?
Just sayin’. 
I bought it for $19.95 at mal-wart a month or two back.