Many are vowing to boycott the event.
One said: "I paid $35 to watch AJ's [Joshua] fight and was super impressed with the spectacle they put on at a sold out Wembley arena, no way am I paying $50 to watch Joe take on a unknown in South Auckland. No way can they justify those costs."
Another said: "Fight someone good and I'll pay, keep fighting bums and I'll find a stream."
Duco's David Higgins told Fairfax that "the people who buy it can feel they've genuinely contributed to funding Joseph's journey.
"Some will complain and whinge about it and others will understand the commercial realities. We don't get any government funding so we don't have a choice.
"It's not all going into the pockets of Dean Lonergan and I whatsoever. It's symptomatic of the costs of running a promotion at this level and pays for Joseph's journey to the world title and staying as holder."
Higgins stressed that the cost is $10 less than for Parker's title fight against Andy Ruiz in December. Anthony Joshua's momentous win over Wladimir Klitschko from Wembley cost New Zealand viewers $35.
Before the Ruiz fight, Sky chief John Fellet told the Herald that Duco controlled of the pricing. He said "the Duco guys are pretty smart" in maximising profit, but admitted to some concerns about prices reach a tipping point.