It would appear that BioShock 2's Sinclair Solutions Tester Pack DLC, now available for PC, Xbox 360 and PS3, is already on the retail game disc. Purchasing the DLC initiates a small file download which is assumed to simply unlock the previously hidden content.
According to users on the 2K forums, the Xbox 360 download is 108KB, while the Games for Windows DLC is a mere 24KB.
2K is charging 400 MS Points/£3.19 for this pack.
The general reaction from fans of the game hasn't been positive, most feeling 2K has held back content which was ready when the game shipped in order to cash in on it later.