How much does it usually cost to replace ignition in 2008 Mercury Mariner?

The ignition is worn out. You can fix this issue with tape. Take ignition out look at end that goes into collum. There should be a half round piece at the end. This is what turns the ignition to start. Take a piece of electrical tape and wrap the end 1 and a half times and trim the excess off the end. When you place it back in the collum it should be snug, not too loose or tight. This should hold a while until you get creative with different tapes and glues to hold better. Summer time will loosen the tape but this is a much cheaper fix then having to buy a new ignition every year. God bless