Thanks for getting in touch!
While we cannot give you any ballpark figures as they may change, you are right in stating that you won’t be eligible for the Medical Card. Reserved for those on low income or social welfare, as retiring expats you will probably be applying for private health insurance.
However, you will be entitled to some subsidized services if you qualify as ordinarily resident. That is, if you’ve lived or are living in Ireland for at least a year. There’s a good chance you will continue to have to pay outpatient costs. There are also schemes that may cater to you depending on whether you have chronic illnesses.
The best place to start would be http://www.citizensinformation.ie/en/health/health_system/entitlement_to_public_health_services.html while there is also a fairly basic summary of things on https://techlifeireland.com/irish-society/healthcare-in-ireland/.
Hope this helps.