That's not even mentioning that terrorism is actually extremely cheap to pull off

One of the common arguments in favor of Bush's taking down Saddam Hussein was that he was financing terrorist groups, and that taking him down removed a large pillar of support from their operations. So we did. And it hasn't seemed to stop them from blowing shit up just fine. So where are they getting their funds from?

Us.

Iraq's deadly insurgent groups have financed their war against U.S. troops in part with hundreds of thousands of dollars in U.S. rebuilding funds that they’ve extorted from Iraqi contractors in Anbar province.

The payments, in return for the insurgents' allowing supplies to move and construction work to begin, have taken place since the earliest projects in 2003, Iraqi contractors, politicians and interpreters involved with reconstruction efforts said.