According to Marc Ambinder's blog, Brownback spent about $600,000 on Ames.
There were 14,302 ballots cast, about 9,500 fewer than were cast in 1999. Some analysts have suggested that this is because McCain, Fred Thompson, and Giuliani boycotted the straw poll. I don't buy it: put the drop in Ames attendance in context with the Democratic candidates massively outraising the Republicans so far in the dollar primary, and you have two data points that back up a point Ron Paul has been making: Americans are abandoning the GOP in droves, and it's mostly because of the war. The only Republican who can win back most of those voters is the only antiwar Republican -- Ron Paul.
Addendum: I should note that the Politico story I link to in the paragraph aboves mentions that Huckabee bought 1,850 tickets for the straw poll -- more than twice what the Paul campaign bought.