The two boxers are due to share around £150m from the fight, which will be held at the MGM Grand Garden Arena in Las Vegas on Saturday.
However, Mayweather is due to claim a 60-40 share of the purse, and the American believes that his Filipino opponent has not been looked after for the bout.
"Financially, he hasn't been treated right for this fight, and [this fight] is all about the money," Mayweather told reporters.
"Saturday is just work, I'll just do what I do. But I'll make upwards of $200m (£130m) for this fight, which is $50m (£33m) apiece for my kids. So it was a smart move."
Mayweather is favourite to win the fight due to his unbeaten run of 47 professional bouts.