Not if his current contract doesn't have a buyout clause or it's ridiculously high. This way he'd get a nice pay increase, play in a system that's suiting him well for a manager with potential to be a top, top manager( more than likely end up at Barcelona in the future).
If he got a buyout of £50m-£60m inserted into a new deal then it doesn't price him out of the top tier of clubs.
He doesn't have a buyout, it would have been widely reported if it did.
Everton are not fools to add a release clause, and they are not common in the UK anyway. The way footballer prices are moving up and up, it'd be stupid to add such clause for anything other than silly money. It would be over £100m easily and thus no worth renewing the contract for. Remember even 1-season wonders like Belotti in Italy have €100m clauses.