From initial application to permanent residency it costs around £6k in visa fees and around £5k in health surcharges over the course of 5 years. Citizenship is another ~£2k all in.

You make three applications with those fees divided slightly differently each time.

That’s without any legal fees if you need someone to help you prepare your application which will be ~£2k per application.

If you have non-British children or stepchildren (which is generally quite rare) it’s approx those fees per kid as well.

For most other European countries including Ireland the fee is <€500.