Mention to him that he best hope he did not mess up any pistons. It is my understanding that the reason it may need the valve job when a TB breaks on an "interference" engine is that the valve tries to be at the same place as the piston at the same time. The mech. is making sure he quotes high enoughto cover his butt. $1600 does not sound too off base. I would rather hear the high price versus being told $500 and then it taking $1600. I have an old saying "Bad news known early is better than bad news known late".
'97 Honda CRV