If EI fly 3 million pax from Dublin and an increase of €5, it means they have to try and recover that from Pax, IF they can, if not they in the hole for €15 Million per year. That would be on 30% of their total passengers numbers. So cost €1.5 per passenger spread through all passengers.
Conversely, if FR slash services as a result of increased charges (not an option for EI), that would have an upside for EI in terms of competitive pressures.
Sounds like neither EI nor FR will have much clout here ...