My car runs good and the only issue is a ticking that won't stop. on 2005 Mazda Mazda6

o you think it will be expensive to repair?
have tried STP and other lubes but issues continue.
Help !!!!! Want to sell car but can't with ticking noise.

Asked by for the 2005 Mazda Mazda6
If it has adjustable valves then needs done. What does your owners manual say about the required maintenance? If it recommends adjusting the valves at 60-90k intervals or even as early as 30k, then start there and see if noise goes away.