Haaland has a release clause of around 65m next summer, if there's club willing to offer 120m now, I am sure Dortmund would be tempted to sell.
Mbappe contract is going to expire in 2022, its reported he may not extend it, and could as well sit out the remain of his contract, which means PSG may risk losing him for nothing. Truth is, no club could afford to pay more than 120m for one player in this market anyway. Even there's no offer this summer, next summer his price would drop significantly, as he would cost nothing in a year time by then.