The Belgium international is currently enjoying his third consecutive year on loan at the Liga high-flyers from Premier League title contenders Chelsea.
Courtois left Genk to sign a five-year deal at Stamford Bridge in July 2011, but he has been unable to usurp Petr Cech as the club's first-choice goalkeeper.
Chelsea are understood to be keen on retaining the 21-year-old's services, though rumours have suggested he could move for a fee in the region of €26million.
And Simeone believes the youngster would represent value no matter the cost.
"For me anything we pay for Courtois is cheap," he said.
"He's a young guy with a huge future and is on track to be one of the best goalkeepers in the world.
"Signing a goalkeeper of his calibre would be a big step. It won't be easy. It depends on what Courtois wants.
"We know what the club needs to do but it's not up to us, he's not our player."
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