Overall, football's quadrennial showpiece has been a bonanza for bookmakers due largely to the relatively early departures of England and Brazil.
However the sparkling displays by 35-year-old Messi driving on his team in what is his last chance to lift the trophy has put the frighteners on some bookies.
William Woodhams, CEO of the world's oldest bookmakers Fitzdares, said a little part of England will be flying the French tricolour on Sunday.
"We are dreading a Messi goal and an Argentina win," he said.
"We need Mbappe to score more goals than Messi and France to win. We will all be French on Sunday."
Woodhams said Messi had become the punters' favourite at the expense of Mbappe even though they both enter the final tied as joint leading scorer with five goals apiece.
Mbappe has failed to score since a double against Poland in the Last 16 match.
"All the money has been on Messi as the Golden Boot winner," said Woodhams, referring to the trophy for the World Cup's top scorer.
"Before the tournament the smart money was on Mbappe but people have seen an opportunity on Messi and pulled in.
"If he wins the Golden Boot it will cost us Â£500,000 ($608,000)."
David Stevens, head of public relations for Coral bookmakers, said it was impossible to split the two sides, which "suggests we could be in for a thriller."
"With so little between these two teams in the betting, it would be no surprise to see this final go all the way to penalties, and there could be worse bets then the 4-1 that this ends with a spot-kick shootout," Stevens said.
Argentina have shown great resilience since losing their opener against Saudi Arabia.
However, they have also evoked memories of overly physical Argentina sides, especially in the bad-tempered quarter-final victory over the Dutch.
As a result punters have piled in on bets on the number of yellow cards the Argentinians will receive on Sunday.
"It's a popular market and we'll be hoping the Argentinians calm down," said Woodhams.
"Lots of people have 4.5 and above yellows."
All the bookmakers interviewed agreed that with several shock results, highlighted by Morocco's historic run to the semi-finals, it has been an excellent World Cup for their trade.
"Any bookmaker that has cause to complain about this World Cup would make Ebeneezer Scrooge blush!" said Stevens.