Licensing the engine (Score 4, Insightful)

While undoubtedly HL2 will sell alot of copies a good deal of the money that has gone into its development has been spent on ensuring the engine itself will be the a strong commercial proposition.Developers have already licensed the HL2 engine, including Arkane (creators of Arx Fatalis).

On top of that further investment has been sunk into Steam which Valve are pushing as a seperate product.

In general the investment in HL2 has not simply been investment in a single game and return on the $40 million invesment will not be measured against retail and steam based sales of the game. Valve are looking for long term predictable income streams generated through licensing the engine, licensing Steam and subscriptions through Steam.

This is why, IMO, they have been pushing back the release dates. With so many different future revenue streams relying on a succesful release they want to make certain the technology is properly showcased and the supporting technologies work free from glitches.