The Irish province take on Toulouse at Tottenham Hotspur stadium on Saturday week, May 25.
Thousands of Leinster fans making the journey face huge price increases getting to and from London with Ryanair and Aer Lingus.
An Irish Independent price survey of the flights – from Dublin to London Stansted with Ryanair and London Heathrow with Aer Lingus – show the airlines are charging up to 400pc more than the same flights the week before.
Supporters hoping to fly from Dublin to London Stansted with Ryanair at 6.20am on the morning of the game, and returning the next day at 12.10pm, will now pay €541.88 for a basic fare.
Ryanair’s flight from Dublin to Stansted this Saturday, departing at 11.35am and returning on Sunday at 1.05pm, costs just €112.03.
With Aer Lingus, the difference is even more stark. Leinster fans travelling with the airline from Dublin to London Heathrow at 9.45am on the morning of the game, and returning the following day at 6.45am, will pay €807.50.
The same flights this weekend will cost €273.90, a difference of €533.60.
Many flights for the weekend of the Champions Cup final are sold out with both airlines.
The only available return flight from London Heathrow with Aer Lingus the day after the game is at 6.45am.
Michael Kilcoyne, chairman of the Consumer Association of Ireland, said consumers were “a long way down the list of priorities” for airlines.
“The kind of price increases we are seeing in this instance amount to several hundred per cent increase,” he said. “It is a huge amount. It cannot be justified.
“This is the same practice we see with hotels when there is a big event and they jack up the prices.
“We are an island nation so we are limited in our choices of how we can go abroad, so airlines are in a position where they can more or less do what they like.”
Fine Gael councillor James Geoghegan is a Leinster fan. He said he has been hearing complaints about the issue for weeks.
“It is a really disappointing situation for fans,” he said. “I know many people were delighted to hear the game was in London as it seemed more accessible to fans.
“But it is proving to be a huge cost burden now and people are paying anything up to €1,000 for flights and accommodation. It is hugely frustrating.
“I am hearing hotel prices are astronomical too. I’ve heard of people flying to the UK midlands and they are getting a train to London to try and offset the cost.
“It’s a massive shame. Leinster fans have proven time and again how devoted they are. The game in Croke Park sold out within hours.
“Unfortunately, the cost is so prohibitive now it is proving too much for many fans.”
Ryanair and Aer Lingus have been contacted for comment.