Consider biting the (750 grain) bullet - figuratively - and handloading for the .50 BMG as early in the game as possible. At $8-10/round for factory ammo, the savings add up fast. A dedicated press is required, but if you don't have a press already, buy a .50-compatible one and you have a wide variety of applications for it.
Ryan sells .50 BMG primers, H50BMG powder, and projectiles (Hornady AMAX), or pick up some surplus .50 BMG pulled projeciles as I do, and pull 'em through a Lee 0.51 bullet sizing die to scrape off the pull marks and you're good to go for $2.50-$3.50/round. Do the math for your application.
Are you saying I'm a "gun nut"? I prefer the term "Firearms Enthusiast"...