Ya I agree with you on that. My 2003 2.8KB Cobra had over $5,000 in performance mods and probably had the traps to get into the 9's. Then you get into the issue of swapping a SRA and suspension mods along with wheels and tires. I find it hard to see an 03/04 Cobra going into the 9's with just $5,000. It'll probably have the power for it but not the correct suspension setup.
As for the 2013. Just because your optioned out car came out to over 68K doesnt mean a 2013 GT500 MSRP isnt 54,xxx. I didnt pay anywhere near 68K for mine.