After the Mexican shocked the Briton in New York in June, immediate talk of a rematch instantly built hype and excitement.
Joshua's defeat therefore has enabled him to profit further, more than doubling his previous career-high payday in New York of £18m.
Joshua is now set to pocket at least £46m, which will catapult him above the previous highest-earning Briton: Ricky Hatton.
The Hitman earned £20m to fight Floyd Mayweather in 2007 in Las Vegas.
While Ruiz is set to earn more than £10m, again, around double his initial £5m as a stand-in opponent to save the initial card at Madison Square Garden after Jarrell Miller failed a drugs test.
The eye-watering purses have been made possible by £31m site fee in Diriyah. And the fighters' pay packets could grow further after the final numbers arrive for pay-per-view, with Sky Sports Box Office charging £24.95.
A record number is expected, according to Eddie Hearn, meaning around £30m more will be added to the pot.
Joshua is aware of his worth too, having discussed how his purse is watered down.
He said: “When you look at it, it’s like, you earn £100, you pay a lot to the tax man, a lot to the trainer, and before you know it you’re left with, in reality, 30 or 40 per cent.
“So it’s not what it really seems. You have to manage yourself and not get flustered about what you think is yours, because 50 or 60 or 70 per cent of it isn’t."