A common estimate I've seen is that roughly 500 extra people a year die due just to the added security costs post-9/11.
A little googling finds a few relevant popular-press articles including these:
http://www.businessweek.com/articles/2012-11-18/how-airport-...
http://www.wired.com/2012/04/is-airport-security-killing-500...
One of the relevant academic papers is by Cornell University researchers Garrick Blalock, Vrinda Kadiyali, and Daniel H. Simon, “The Impact of Post-9/11 Airport Security Measures on the Demand for Air Travel,” published in The Journal of Law and Economics in November 2007. (pdf here: http://dyson.cornell.edu/faculty_sites/gb78/wp/JLE_6301.pdf )