"troops and mercenaries"
Among the many advantages to the Bush Regime of outsourcing the military is that it makes it easy to obfuscate the actual force levels and expenditures. You scoff at 300,000, but can you come up with an accurate total for the number of troops and mercenaries?
Wikipedia puts it this way:
It is estimated by the Pentagon and company representatives that there are 20,000 to 30,000 armed security contractors working in Iraq, and some estimates are as much as 100,000, though no official figures exist.
Blackwater Worldwide
If 100,000 is the correct figure, the total is in the ballpark Bowser stated. If you know the actual number, you ought to tell the world.