Since less than 1% of the population has an annual after tax income over $100,000.....I am not worried about huge databases. In my part of the country the really big spenders are not flashy....in fact the richest man I know with an annual income of millions of dollars...doesn't carry cash at all.
Also I think it is more reasonable to look at what we know the terrorists did to predict their future behavior than to say well they could have done it without spending the cash...yes, they could have, but they didn't...and that is exactly the point.