Khan is reportedly chasing a blockbuster clash with Floyd Mayweather, and while Hearn acknowledges that the Bolton fighter would earn more money from that fight, he believes that a domestic showdown with Brook is Khan's next best option should he not face the unbeaten American.
Hearn told Sky Sports News: "Everybody wants the Khan fight. Khan will want the Mayweather fight of course and I think that's likely to happen. If it doesn't, I think Khan against Brook becomes a real possibility.
"I've always mentioned it to Amir and I've told him it's a huge money fight. It's by far the biggest payday of his career, by far, but it doesn't equate to the same kind of money as the Mayweather fight.
"That's the one he will be chasing. I spoke to Richard Schaefer (CEO of Golden Boy Promotions) just a couple of days ago about Amir Khan and Adrien Broner and said there is big money in this fight. I believe that it's a box office fight and I believe that it would sell 30,000 tickets at Bramall Lane or wherever that may be."