The welterweight rivals, both 30, had been in talks to fight for Brook's IBF title in May but could not agree on financial terms.
Hearn said he offered a 50-50 split but added Khan called for 70-30 because "he feels he is the bigger name".
"When someone puts 70-30 on the table, it puts up boundaries," added Hearn.
"The communication lines are open but it's just the perception of what the split should be between the two camps is too wide."
Khan, who has fought in nine world title bouts, wrote on Twitter: "Eddie I'm the A side. Don't you agree?"
The former light-welterweight world champion added: "70/30. You both will make a lot of money."
Bolton's Khan stepped up two weight classes to challenge Mexican Saul 'Canelo' Alvarez and suffered a heavy knockout defeat in May 2016, while Brook met the same fate when he stepped up two weights against middleweight king Gennady Golovkin in September.
"I think Amir Khan is a bigger name than Kell Brook but Kell Brook is the world champion," said Hearn.
"Kell is coming off the back of a loss and Amir Khan got knocked out badly in his last fight so I think 45 or 55 percent one way is a reasonable range but he might take the fight later in the year."
If the two fighters do come to an agreement, Hearn suggested that the match-up has the potential to make a great trilogy.
"I think Amir Khan has got three or four fights left," he said.
"Three of them could be a trilogy against Kell Brook because I think they would all be fantastic fights. They are 50-50 fights so the purse should be too."
Negotiations for an all-British super-fight between Amir Khan and Kell Brook were halted by a purse split, says promoter Eddie Hearn.