Earlier this year when the long awaited Metro in Dublin was announced, it came in at an estimated cost of €3billion. 

However earlier this week when launching the National broadband Plan, Taoiseach Leo Varadkar seemed to suggest the Metro could cost 4 to 5 billion; significantly more. 

So, just how much will the project cost? 

We ask Edgar Morgenroth, Professor of Economics in Dublin City University.