I honestly don't know what price that would be, its not a common job. Have done 75% of that job on a Volvo, and it does take a hell of a long time to get in about those engines though, so imagine the labour would be pretty big. We usually just get heads reconditioned instead of buying new ones or second hand ones, but it can be dependent on exactly whats happened to them.
It sounds like the Alternator belt has broken/come off, been sucked in behind the Crankshaft pulley and jammed it up, which has caused the timing to go out, and your valves to hit the pistons. The engine would turn if they're bent enough, but it wouldnt run. The "rough" feeling would be it pressing against the bent valves, probably feels like the engines about to lock up but just puses by the "tight spot".
Its not uncommon on Volvos, sadly. Never seen it with a new belt tbh, but if it was faulty workmanship then it wouldve shown before now, unless you've only done ten miles?
And the Camshaft wont have come out the head, its stronger than the valves which would break/bend before the Cams broke (unless something far more serious occurred). The cams will have to be removed to sort it though.