Free buses for people attending the Papal Mass in the Phoenix Park cost almost €600,000.
The National Transport Authority made the payment to Dublin Bus, which revealed the sum in its latest annual report.
The Irish Times reports that the State-owned company increased its profits to €3.7m last year.
It had revenues of €263.3m and a surplus of €3.7m.
The number of passenger journeys also rose by 4.1 million to a total of 143.5 million.