"In the history of betting, certainly since it was legalised in 1961, a [single event] winner with odds of 5,000-1 has never happened," says Simon Clare from the betting firm Coral. "Every bookmaker is crying out in pain.
"That's a barometer of what Leicester have done and just how amazing this win is."
Jessica Bridges from rival Ladbrokes agrees.
"This is the biggest sporting upset of all time. We've all got a bit of egg on our face."
Bookmakers have been cheering Leicester's success, whilst simultaneously putting their hands in their collective pockets.
William Hill has paid out more than £20,000 to 39-year-old carpenter, Leigh Herbert.
He was one of the canny few to take up the now-famous odds of 5,000-1 for his team to win.
Although he has been a supporter since he was 10,  he doesn't usually put his money where his heart is.
But, mulling over their prospects on a camping holiday he found he was encouraged by the team's performance at the end of last season, and, taking a shine to the appointment of Claudio Ranieri as manager, he decided to put down the £5 bet for his team to win.
"I thought, they're going to do something special this season," he says.
"I really enjoyed the first half of the season, the second half just got harder and harder.
"I would feel sick watching them play."
Eventually, he cashed out £2 of his £5 bet, making £5,600, but left the £3 remainder in place, which eventually won him £15,000. A big party is in order this weekend - as well as house hunting with his new deposit.
Bookmakers, like Coral, estimate the industry as a whole will have paid out around £20m over the title win. Coral themselves lost £2m.
But bookmakers won't have lost out overall, admits Ladbrokes' Alex Donohue.
Although Ladbrokes are losing £3m on Leicester this week, throughout the season a lot of bets were placed on the favourites, such as Chelsea and Manchester City, which will have more than cushioned the blow.
"£3m is a record net payout for a title winner, but we did well out of Leicester upsetting the odds to get there. No complaints at all," he tweeted.
Ladbrokes are "by no means crying out in pain" over the season in general, says Mr Donohue.
Bookmakers do best when a second or third favourite team wins the title, he says.
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More importantly for bookmakers Leicester's win is a great story.
The bookmakers were much slower than the punters to believe that Leicester could win the title. The problem was not so much the long odds at the start of the season, but the fact that they were so slow to respond to Leicester's success.
At Christmas, when the Foxes were unbeaten for 10 games in a row, the odds were still quite high, in Coral's case they were still at 33-1 in December.
It wasn't until Leicester beat Manchester City 3-1 in February that they became favourites to win.
"The bookies were just ignoring their form. The punters started to believe but not the bookies," said Mr Clare.
"We've never lost money like this - it's the biggest hit we've ever taken. In a way it's a beautiful wake up call. It's an amazing moment."
And there's a sound reason they are not downcast at their losses.  Next year they're expecting a great flood of new bets as fans from Burnley to Bournemouth hope that their team will "do a Leicester".
The odds on a Watford or a West Brom win are slight of course. Leicester's success was  a "perfect storm of the right manager, right players, few injuries, no playing in Europe and the big teams underperforming" says Dale Tempest from online betting firm Skybet.
Skybet, which sponsors the three divisions below the Premier League, has a particularly large base of Leicester supporters and is therefore one of the companies that stands to lose the most - in the region of £5m.
Interestingly, the bookmakers seem to think that the chances of Leicester being relegated are greater than them winning again.
Mr Tempest says that's because the stakes have been raised - there will be tempting offers for the top players, the big teams are looking to change managers and they'll have to play in Europe.
So has it made the industry more cautious?
Ladbrokes says no more 5,000-1 odds for the Premier League, Coral says it will be much more cautious.
But Skybet have got 5,000-1 odds for Burnley to win the Premier League, who have just won the Championship and will be promoted next season. Already, 888 people have placed their bets - meaning that if they win Skybet stand to lose £7m.
However, Mr Tempest says the company will be quicker to slash the odds should the team start performing, a sentiment echoed by all the companies.
But William Hill's Graham Sharpe says this is a numbers game. The chances of Leicester winning were that slim and they would probably do the same again - and the next 4,999 times they'll be right.
He likens it to the jockey Frankie Dettori riding the winning horse in all seven races at Ascot in 1996 - an unheard of feat. He remembers the stunned haze surrounding the bookies and their £40m loss.
But he says, it was so unlikely, that they all agreed they'd probably do the same again.
"This time we hold our hands up and say well done. But Ranieri, don't do it again," he says.
And as for Leigh Herbert - will he be doing it again?
"This is it for me. I mean... it's not going to happen again, so why carry on?"
I wonder if he will stick to that.
The betting industry is licking its financial wounds.