Sane played more minutes than Mahrez and he was the one Pep relies on when we need a goal, he usually the first to come from the bench ( Schalke, United & Liverpool ) if I remember correctly.
He had a dip in form recently, but thats can happen to any player who isn't playing regularly.
Real Madrid are willing to pay around 100m for Hazard who is 28 years old with 1 year left in his contract, next year Sane will be 24 with 1 year and I think his value will not drop and if "God forbid" we have to sell, we will get more than 80m.
Barcelona will be fed up with Dembele, Malcom and maybe Coutinho, Juventus may want to replace Ronaldo with another star, there could be more clubs willing to compete for his signature.