Chelsea boss Jose Mourinho has conceded it may take a huge fee to prise Everton defender John Stones away from Goodison Park.
The Premier League champions had a bid reported to be in the region of £20million rebuffed by the Toffees last week, with manager Roberto Martinez criticising the Blues for the way they handled their approach.
Unperturbed, Chelsea are expected to up their offer for the 21-year-old - who they view as a long-term successor to John Terry - but Mourinho knows Everton will not let him go without a fight.
"That is the market now," Mourinho explained.
"You only pay it if you want to. If you don't want to pay it, don't pay. It's as simple as that.
"The market has no rules or limits from season to season."
After the summer departures of Sylvain Distin and Antolin Alcaraz, Everton's defensive numbers are already on the light side and Martinez has insisted he is not interested in selling any of his stars.
But Mourinho, who has risked further upsetting the Merseysiders with a "smaller club" comment, is determined to test that resolve.
"It's a good market. That's why smaller clubs, if they have interesting young English players, they use that in the right way for them," he said.
"I don't criticise them. They play the market for themselves. If the big clubs don't want to go over certain limits, they have to make a decision."
Everton and England's John Stones in pictures: