From Wikipedia: >> The 9/11 Commission stated in their final report that the "9/11 plotters eventually spent somewhere between $400,000 and $500,000 to plan an

From Wikipedia: >> The 9/11 Commission stated in their final report that the "9/11 plotters eventually spent somewhere between $400,000 and $500,000 to plan and conduct their attack" Still a non-trivial amount of financial support.