Successful defences of his title are likely to reap the 24-year-old Mangere-born fighter the lion's share of available purses each time with WBC champion Deontay Wilder being lined up as Joshua's next opponent if he beats Klitschko.
But if Parker can continue his steady rise to prominence and secure a partial or full unification bout across the heavyweight division, his earnings will sky-rocket.
The London Telegraph has revealed the Joshua-Klitschko bout, set for next year in England, is expected to gross £30 million ($NZ53m) with the two fighters expected to share £18 million ($NZ32m) between them.
Joshua's IBF belt, the vacant WBA title and also The Ring Magazine belt will be on the line when the pair meet at Wembley Stadium on April 29. Promoters are optimistic that there will be more than a million pay-per-view buys with Wembley also set up for 90,000 spectators.03
Joshua agreed to the fight only hours before pummelling Mexican American Eric Molina in just three rounds last weekend.
"If I beat him (Klitschko), people will say he is past his time, AJ is great, or if I lose then people will say 'this guy is a hype job'. It is just a fight. If the winner is the No 1 heavyweight then I will still have to go prove it again, and again, and again, and again.
That is why it doesn't mean anything," he said.
"You can't just build yourself up and get carried away. Beat Klitschko, then they say you have to beat David Haye, then Luis Ortiz, then Tyson Fury comes out of retirement. Chill, keep grinding and then one day we can look back and I can show you a different side. That is a long way away."
Joshua's promoter Eddie Hearn believes the fight will bust records.
"Capacity-wise, for sure," he said. "This is a unique fight, two ¬Olympic champions, two guys at different stages of their careers. We've got the hottest prospect in world boxing against a legend in the heavyweight division."
Beating the 41-year-old Ukrainian, who reigned the heavyweight division for nine-and-a-half years, will elevate Joshua to new levels.
Hearn said: "Once you've had a fight like Wladimir ¬Klitschko and you earn what you earn from that fight, you can't go back into a voluntary defence against just somebody or even a mandatory defence. It will be very difficult to maintain all the belts."
Hearn believes Joshua will knock out Klitschko. "I think after Wladimir Klitschko, the fight is Deontay Wilder [the WBC champion]."
Klitschko has refused to comment on Tyson Fury in the last week, in spite of being repeatedly asked about the exiled heavyweight who defeated him 13 months ago.
"They're not difficult to deal with, but they've been burnt, so they are very diligent in what they do," explained Hearn. "That's why it took so long because they want to make sure every box is ticked because they have had an unpleasant experience."
- Staff reporters and Daily Telegraph
