enough bs..... the cartridges for the .50 BMG do NOT cost 12 dollars each... you can buy surplus ammo for about 1.30 to 1.50 each. Hardly more than premium ammo for a .338 Win mag... Now, if you want target grade ammo, you will pay more, but certainly not 12 dollars each. You can buy a Barret semi-auto for about 7,000 dollars, and the bolt action single shots for around 2,000 and up.
RidgeRunner is correct... Gunnery Sgt. Carlos Hathcock started using the .50cal M2 machine gun, in semi-auto mode(I think) in Viet Nam as a sniper weapon... and for a long time, he held the record for the longest killshot... but I have heard that record has been beaten many times in Afghanistan.... different war, different location..
Comparing the .50 to the .30-06 is meaningless... like comparing a Chevy Cavalier to a AA fuel dragster... completely different tools and purposes.
RIP White Feather........

"Progress, far from consisting in change, depends on retentiveness..those who cannot remember the past are condemned to repeat it." Santayana