These two subjects are not the same.
Tavares went all the way to UFA and was the best of his class and had competing bids from other teams in hand. And still left $3M on the table, for the record. If Matty wants to go that far and let the next 12 months speak to his value, that's his right, but then he also assumes the risk of having a shit year or getting catastrophically injured.
If he doesn't want to take that risk, there should be a discount. And if he wants to sign now, he's doing it in a year where he was a 94 point player and McDavid put up 153, and several other players scored over 50 including Pastrnak who scored 60 and just signed for $11.25m, so what is the basis for being the highest paid player in the league - because he's a center? Okay, but he's a center with zero playoff success, unlike Pastrnak and others. And McDavid is a center too, signed for $12.5m for the next three seasons still, which, if Matty signs for only 5 years, should serve as a cap on him frankly. Beyond all that, how much money is enough? Does he need to be highest paid for bragging rights - most expensive loser? Because he'll be eating up dollars that can go to better supporting players instead of more ZARs, so he needs to decide if a cup is what he really wants or not. He can already buy whatever the hell he wants for the rest of his life, but he's only got around 5-10 years to establish himself as a winner.