I still like to think that money talks...(or the threat of withholding money).

As someone said to me just the other day, money is a social construct. The government doesn't actually pay their suppliers with anything of intrinsic value. They cause computers to send some electrons to someone else's computers in a way that we collectively agree to pretend represents a transfer of real value.

If the companies that supply beans, bullets and band-aids (to steal a phrase) decide to keep sending actual stuff to the troops, with the (so-far) certain knowledge that they'll eventually get one of those electronic transactions in their favor, this can go on indefinitely. The administration is basically saying, "The troops are there, we have to supply them. We've sent the supplies, we have to pay for them."

When (I'm guessing) Rove read the part of the Constitution that says (paraphrased), "The president can send troops, then Congress has to pay to keep them there," he interpreted that as, "The president can send troops, then Congress has to pay to keep them there."