The veteran South Sydney coach said the NRL had also disadvantaged next year's entrants Perth, claiming prospective recruits would be in for an easy decision in choosing between the two forthcoming expansion sides.
Tweaks to Australian tax laws expected in this month's federal budget will mean players and staff at the Chiefs do not pay tax on their salaries.
The move was designed to entice players to the Government-backed team, which is seen as a means for Australia to strengthen diplomatic ties in the hotly-contested Pacific.
This week's signing of four-time premiership winner Jarome Luai was the first marker of the Chiefs' potency on the player market.
The last man to coach an expansion side in its first season, ex-Dolphins boss Bennett voiced his concerns on Saturday.
"They've got a hell of an advantage. They've got a different salary cap to the rest of us," he said.
"When the Dolphins came in, we didn't get one exemption from the game. Personally, I think that's really unfair."
The exact salary cap for 2028 will be determined by the next collective bargaining agreement between the league and its players, but will sit above $12 million for a top-30 squad in the Chiefs' first season.
Playing contracts must be registered and approved by the NRL, which would not sign off on the Chiefs low-balling players on the understanding they would dodge tax.
But Bennett said the tax-free salaries were nevertheless an enormous bargaining chip.
"There's going to be a blow-up somewhere with it because clubs have worked really, really hard to develop players under salary cap pressure," he said.
"(They) are going to find it just about intolerable to see their players leave when they can't give them the same deal that you can get somewhere else because of the salary cap exemptions."
Bennett felt the other victims were the Perth Bears, based in AFL heartland and playing their first season next year without any extra assistance from the NRL.
He worried for Mal Meninga's ability to recruit players in the shadow of the Chiefs.
"It's tough having to go from zero without any support from the NRL," Bennett said.
"(If I'm a player) I'm thinking about going to the Bears, I'm thinking about going to Papua New Guinea, I can get the same money in Papua New Guinea but I get a benefit that I don't have to pay tax on it. It's not going to be a hard decision that way.
"I just don't know how the game thinks they (Perth) are going to be as competitive as they want them to be when you've got another team in another place buying players at a different price."
PNG international Alex Johnston is expected to become the Chiefs' second signing after triggering a clause in his Souths contract that permitted early negotiations with the Port Moresby side.
"I'm really pleased for him," Bennett said.
"He's at the end of his career, he's not starting it, so he hasn't got a lot of time but it'll be wonderful for him. It means a lot to him."
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