Growth in a resurgent united Ireland would quickly replace British government funding, Sinn Féin's deputy leader has said.
Michelle O'Neill said unity would add 2 per cent to the debt of the island but predicted a sharp rise in living standards in Northern Ireland.
Republicans believe Brexit and the prospect of the north being taken out of the EU against the will of a majority in the referendum has revitalised the case for a united Ireland.
The annual cash transfer from Great Britain for running public services was considerably smaller than widely estimated, at around £9.2 billion a year, Sinn Fein's vice-president said.
Read More: Ireland on path for dual north/south referendums on unification
She added: "I believe it is perfectly manageable and the benefits are substantial."
Post-Brexit and over eight years, gross domestic product would receive a €25.5 billion boost, the Sinn Féin leader added.
"That is a hugely significant figure in terms of the benefit that could be accrued.
"And that growth would be released in a united Ireland.
"It would quickly wipe out the subvention and increase living standards across the island but particularly here in the north where our standards are lower."
On Tuesday she addressed business leaders at a general election hustings meeting organised by the Northern Ireland Chamber and hosted by BT in Belfast.
Sinn Féin is aiming to defend its seats and win North Belfast.
Its anti-Brexit candidate John Finucane, a lawyer, son of murdered solicitor Pat Finucane and Lord Mayor of Belfast, is bidding to unseat DUP deputy leader Nigel Dodds.
Mrs O'Neill again urged the Dublin government to convene an all-island forum on planning for unity, a measure Taoiseach Leo Varadkar has said would be provocative.
British prime minister Boris Johnson has repeatedly stressed his commitment to the constituent parts of the UK and the British government has given no indication that any poll on unity is being considered.
His proposed Brexit deal would involve new bureaucracy and checks on goods crossing the Irish Sea for firms in Northern Ireland to avoid any border on the island of Ireland.
