I have used Hornady's AMAX with very good results in my AR-50, they will shoot MOA or better as long as I'm doing my part.
As for custom or off the shelf solids there are plenty out there, at most matches you'll see most guys using solids. There really isn't much difference in price between AMAX bullets and solids, they usually run about $2 each. The price will vary from where you buy them from and what type of solids you're buying.
Brass will run you from as low as .50 cents to as high as $2 each depending on if you're buying once fired surplus or new. IMI/TZZ brass is considered the best .50 BMG brass but it's almost non existant these days. About the only primer that you can find on the market is CCI 35's. There used to be a few brands but they were imported and no one seems to be importing them anymore.
I see the world thru bloodshot eyes
Streets filled with blood from distant lies
The dogs of war never compromise,
No time for rearranging.