The full cost of the deal that restored the Living Out Allowance to junior doctors is €16m a year - €4m higher than originally projected.
The restoration of the allowance, worth €3,182 annually, was recently agreed in talks at the Workplace Relations Commission with the HSE and the Department of Health.
Junior doctors had earlier threatened to ballot for industrial action.
The allowance is aimed at covering some of the expenses incurred by junior doctors who have to move to a new hospital posting every six months. It was abolished in 2012 for all new-entrant doctors.
The Irish Medical Organisation had taken a High Court action claiming the abolition amounted to a breach of contract. The HSE estimated that 70pc of interns,senior house officers, registrars and senior registrars who would previously have been entitled to this allowance were not in receipt of it.
The full cost of the deal was revealed by Health Minister Simon Harris in a parliamentary response to Fianna Fáil TD Dara Calleary.
It adds further to the pay bill for some public sector workers in a bid to keep industrial peace.
"This restoration will be implemented and funded in the context of the forthcoming public sector pay talks," Mr Harris said.
The payment is now incorporated into salary - which means the basic pay of junior doctors will increase.
All other payments, such as overtime and premium pay, will be calculated on the new basic pay, said the IMO. As part of the deal, a three-month review was secured to deal with the continuing education requirements of junior doctors and the resources required. The review is due to be completed in May.
The only upside for health employers is that the deal does not involve any backpay, which had been sought in the original legal challenge. However, it was parked as the demand would have to be ruled upon by the courts and there was no guarantee that the IMO would win the case.
This would have pushed up the bill for the HSE. The case was struck out and the deal meant doctors avoided protracted legal proceedings.