Agreed. If it were Brighton or Huddersfield in for him the price would probably be lower. The price of a player is determined by what he buyer can afford. The starting price for any player City or United try to sign will be £40M, us probably around £30M.Why shouldn't they? He's their player than can ask what they like.
I have said it before There is no benchmark for what a player is worth only what a team will sell him for, and what a team will pay for him.