They see what PSG, Man City and the classico clubs are giving players, near unlimited salaries with certain players. So your more greedy players see that and demand more.
I'm more suprised about Alaba leaving you over that, he is a Bayern kid basically. While Coman has been a mercenary through and through so not suprised, even if its insanely deluded to think he deserves 12m net. But if he was free agent prolly dumbass PSG would pay it to bring him back home.