Following an article here, https://www.itpro.com/general-data-protection-regulation-gdpr/who-benefits-from-gdpr-fines it seems that GDPR fines go wherever the local country's laws tell it to go. The article focused on UK and how their fines went to their general treasury, which leads me to assume the fines from Ireland just go to the Irish government. But if it's an international fine, who knows.