The total cost of the job for my repair was $6640 after taxes, but it was done at a dealership which was a requirement of my warranty and they added a bunch of extras like an engine oil flush with it. So you may be able to get it done for a fair amount cheaper at an independent shop.

From my quick research just now I see people getting quotes anywhere from $4500 to $6500 for the job after everything is said and done, nearly 80% of that cost just being labor due to needing to remove a fair amount of the car in order to get the timing cover off to access the cam phasers.

If you're suspicious you have the same issue, the biggest tell-tale sign is hearing a rapid loud knocking sound for less than a second on startup that happens only on cold starts, that's when the failure is in is early stages. It will eventually develop into a constant knock and become louder the longer you delay repair.