The official purses for the two men have been revealed and they show that the boxer is pocketing a lot more cash than the MMA star for tonight's fight.
he Nevada State Athletic Commission revealed the purses for each man last night and it shows that the American is guaranteed to take home $100m (€84m) tonight.
Meanwhile the Dubliner's guaranteed take home is ONLY $30m (€25m).
These figures are only the guaranteed purses, with both men likely to take home vast amounts more once money from pay-per-view buys and sponsorship deals are included.
McGregor's pay day is by far the largest guaranteed of his career and significantly larger than any earned by any MMA fighter.
Mayweather was guaranteed $100m for his much hyped fight with Manny Pacquiao in 2015 but he ended up making in the region of $250m (€209m) once he got his share of the other revenue sources.
ESPN estimate that he will again pocket well over $200m for tonight's fight.
As for McGregor, ESPN estimate that the Dubliner's take will exceed $100m (€84m).