Safari Club International members include Walter Palmer, the United States dentist infamously responsible for the death of beloved Zimbabwe lion Cecil on what he claimed was a legal hunt - and the auction has raised the hackles of animal rights groups.
Humane Society International spokeswoman Wendy Higgins said the auctions raised money for the club's pro-hunting activities.
Last year, $2.7 million was raised from the auction of 314 donated hunts.
"Offering pay-to-slay hunting trips is grotesque, treating these magnificent animals as little more than living target practice," she said.
SPCA chief executive Ric Odom said the society did not have an issue with hunting for food or as part of pest control.
But it was against trophy hunting, especially by amateur hunters who might not have the skill to kill quickly.
"The whole idea that people are going out and shooting animals for their own entertainment, that's pretty distasteful, and I think a lot of New Zealanders would agree with that," he said.
Safe New Zealand campaigns officer Shanti Ahluwalia said hurting animals for entertainment was "never okay".
But Safari Club International's New Zealand branch president Mike Knowles said trophy hunting here had been going on for decades.
The Las Vegas auction proceeds paid for hunting and conservation projects, he said.
Mr Knowles believed trophy hunting was worth $30 million a year to the New Zealand economy, and said guides were bound by a code of ethics.
Deerstalkers' Association national president Bill O'Leary said foreign trophy hunters pumped "tens of millions" into the economy each year.
He said Kiwis also travelled overseas for trophy hunting, and he had no problem with people coming here to do the same, provided they hunted with a member of the Professional Hunting Guides Association.
New Zealand hunting safari operators who donated packages for the auction wouldn't comment, but one, speaking on the condition he was not named, said clients were "high-value visitors".
"In a week, just for the hunting, they'd pay $15,000. A lot of them will spend another week or more looking around New Zealand and ... these guys aren't cruising around in a campervan."