The youngster is on loan at the Paris club this term, and has excelled in all competitions.
But there is no option to buy clause, and Everton want a huge fee for Kean.
And according to PSG sporting director Leonardo, any permanent deal would be very complicated to arrange.
Leonardo told France Bleu: "Today, knowing a value is difficult.
"The choice was obvious. We made the choice to take a young player. We took him for one year, then we'll see.
"Everton didn't want to lose him. He plays very well, he scores. He has an important future, but there, we cannot know.
"We could not do anything other than a loan and I think that today having him available for a year is already very positive.
"If we can see the future under certain conditions, we will try to see how it goes, but today, it's very complicated to know."