Well it just depends on what you want. Sometimes you can find a guy selling a used one with hardly any rounds through them. But $750 is about normal considering it is machined and ready to install.
$750 is about the average for providing a barrel, chambering it, coating it, and normally threading the muzzle. On any custom rifle generally......I will say.....GAP has done all the barrels for my AX, they've never needed the rifle......and they are all insane shooters.
And those range from a 6mm Crusader, .243win, 6cm, and a 260rem. All amazing shooters.