The Taoiseach has told the Dáil that the final cost of the National Broadband Plan could be in the region of €3bn, spread over 25 years.
During Leader's Questions in the Dáil, Mr Varadkar also defended the Government's decision to delay the Cabinet discussion of the plan, which he described as a "huge project of huge scale".
"We want to do this, but we want to do it right and before we bring a decision to Cabinet we want to make sure there is no better alternative," Mr Varadkar said.
Mr Varadkar also told Sinn Féin leader Mary Lou McDonald it was on a different scale to the original project which was on a much smaller scale.
"We are now faced perhaps again with a scandalous cost over-run that might be commensurate with the debacle around the National Children's Hospital," Ms McDonald said.
She said the whole process was marked by delay, and told Mr Varadkar that it was astonishing that the head of Government was taking such "a laissez faire view of the final costings".
"You should have a view as to the affordability or the price range," Ms McDonald said.
"The original estimate was based on bringing fibre to 11,000 villages, not fibre to 540,000 homes, farms and businesses," Mr Varadkar said.
He also acknowledged that just one bidder of three remained in the process, but said that each of the bids came in a similar figure.
"We do know what the cost of the project is," he said.