Irrational Games Purchase Price Revealed

After scouring Take-Two's recent 10-K filing, GameSpot is reporting that the publisher was able to acquire Irrational Games for $11.8 million in a mix of cash, stock, and other perks. Considering the success of the company's previous titles (System Shock 2, SWAT 4, and the Freedom Force franchise) and the hype surrounding BioShock, that figure sounds pretty low to me. Or is that the going rate for a successful PC game developer nowadays?