I have used the Armalite AR-50 and it's outstanding...
One of the Wholesalers we've used has run Armalites on special for $3,500. But for no more than I do/did shoot one, that's about $2K more than I wanted to plunk down.
Guy I worked with has a Brother that developed specialized ammo for Uncle Sam, so they bought a Barrett M107 and there was talk of selling it as they weren't really using it anymore.
We had a Bushmaster .50 come into the Shop and I should have, even could have bought it, but didn't.
I have bought multiple Safety Harbor .50's and the only problem I ever encountered was the knucklehead we sold one to managed to break the Bolt handle off, so Walter sent him a new on at no charge...was buying them during our Bi-Annual visit to Knob Creek, but ATF pulled the plug on his Uppers.
Had a "Custom" single-shot of unknown manufacture...heavy was an understatement, 36" Barrel and Bench Rest Stock...shot good, but it must have gone 35 pounds.
Bought two of the BOHICS when they first came out...had problems with light hammer strikes; cleaned up, polished and with a heavier spring (and maybe hammer, don't remember) they shot just fine.
Guess it's because I've got enough stuff and equipment to reload hundreds of rounds of .50 that's pushing me to find another one.