How much does a ignition cost to replace?

It depends on the age of the vehicle as newer cars use a coil for each spark plug, resulting in more expensive labor. It also depends on engines, if it is a V6 or above, the positioning of the engine could be so that three cylinders are positioned towards the rear of the engine compartment (the firewall) in which case you'll be paying more for labor really than parts (it's hard to work back there)

It can cost anywhere from $100 - $500+