The Barret semi-auto comes in at around $10,000 for the kit (case, Swarovski scope, rifle, magazines, etc.).
Spend it on a good AR-10/M-1A W/accessories and lots of ammo. Burn enough ammo on the range so that you are good with it.
N.B.: It will be my assumption that if you are carrying one of those around my neighborhood and I do not know who you are, that you are a bad guy (or an idiot which is the same). Steps will be taken.