Yup, trying to make a barrel from scratch would be problematic. I see barrels at gun shows quit often foe under $200. They are military discards but still useful.
Brownells had brand new ones for $250 for a while.
I have not seen used .50 cal barrels for a bit. I suspect the military is having them destroyed rather than releasing them on the surplus market.
We should see some relieve with a Trump presidency.