How much does it cost to repair valve lifters on a 2003 Lincoln Aviator

What is your question?

I hear a constant tick, tick from the engine. I kind of knew it was the lifters but took it to a mechanic I trust. He confirmed it was the valve lifters. Asked him how much to fix and he said he stop does not do that type of work so he could not give an estimate. It's not smoking so the seals seem good. Wondering how much to repair or replace the valve lifters?