The 40-year-old Gallen, who has just beaten former Manly and Parramatta forward Darcy Lussick by a TKO, claimed that Williams was running from the so-called super deal.
The 36-year-old dual code superstar Williams - who has also retired from football - is unbeaten in eight professional fights, most held in Australia.
Gallen told the Daily Telegraph that his advisor Peter Mitrevski approached the Williams boxing camp about the fight deal, but it was not accepted.
"So I'm f****** filthy," said Gallen, who would no doubt like to lure Williams back into the ring with some public taunts.
"We're talking about life changing money - two fights, $4m each.
"Who else is getting that sort of cash. There are world champions who don't get that money. It's unbelievable.
"So given his response do you think that fight with Sonny ever happens? I doubt it."
There is also talk of Gallen fighting the recently retired British league great Sam Burgess in a $1m deal.
Speaking to Main Event after his win over Lussick on Wednesday night, Gallen revealed he was "without a doubt" going to retire next year, regardless of what Williams decided to do.
"Unless it happens in the middle of next year, it won't happen," Gallen said. "We were offered $4 million each to fight twice next year, and it's not happening. Why? That's unheard of money. It's ridiculous.
"We're not doing it, the ball's in his court.
"I've said for years, 'Let's do it', but there's going to come a time where I say, 'No more". And bet your bottom dollar that's when he says, 'Let's do it'."
