The Oireachtas Joint Committee on Transport has been told that the metro link between Dublin City Centre and Dublin Airport could be built for as little as €595m.
The cost had been estimated by the Rail Procurement Agency at around €4.6bn.
Cormac Rabbitte of the Dublin Metro Group told the committee that the line could be built for €45m per kilometre. He said costs would be reduced by using 'lump sum turn key' contracts.
The Dublin Metro Group approach is based on the cost of recent lines built for the Madrid Metro system.
Mr Rabbitte told the committee that clear thinking and political will contributed to those lines being delivered inexpensively and on time.
He also claimed that relying on underground tunnels would reduce the delay caused by environmental impact studies.
The group suggests a route that would largely run under industrial and public land, in theory minimising the threat of delays in the planning process.
They told the committee that they would like to construct Dublin's Metro, with a 30-year deal to operate it.
Senator David Norris said that he was keen to see the group implement the project.
Fianna Fáil's Peter Power expressed doubts about the figures presented to the committee.
Chairman Eoin Ryan said that the members were used to seeing one set of figures at presentations, but far higher ones on completion.
Labour's Róisín Shortall said that the project would be delayed by at least two years by the planning process.
