The cake, flown in from New York for the November 2007 celebration, is possibly the most expensive ever purchased in Irish history.
At the time of the wedding Quinn was, according to Forbes magazine, the richest man in the country with a fortune put at €4.6bn.
The black-tie and evening dress affair where the cake was unveiled was attended by 400 guests -- putting the cost of a slice at an estimated €250.
The wedding party also made a substantial donation to local charities.
The cost of the wedding was charged to a subsidiary of the Quinn Group in the same way that the August 2010 wedding of Aoife Quinn to solicitor Stephen Kelly was. Aoife Quinn in a TV3 interview this year said she "didn't actually know" who paid for her wedding as "the company took care of everything on our behalf".
The Quinn-McPartland wedding featured Rolls-Royce Phantoms to ferry the bridal party from the church in Staghill to their reception in the Slieve Russell hotel.
The Quinn family declined to comment on the wedding cake or the total cost of the 2007 wedding.
The emergence of the cost of the cake contrasts starkly with the family's current position. They must account for every penny they spend to the courts and Quinn's son Sean Quinn Jr now resides in prison. Next week he will receive news of his appeal to the Supreme Court.
The family is also engaged in other court battles in relation to their overseas property assets. Their main focus, however, is fighting to bring their "big case," against IBRC, formerly Anglo Irish Bank, where they hope to prove that the empire their father built was taken away from them illegally.