I'm sure others will have more knowlegde on this subject than I, but I don't think 9/11 had anything to do with it, it was the 1994 Omnibus Violent Crime Reduction and Law Enforcement Act (Slick Willie's Crime Bill). The cost went way, way up after that, you must do "X" amount of sales per year to be classified a legitimate dealer and you open yourself up to possible (probable) search anytime 24/7 from the BATF.