I know we like to think all Bruins players will take less to stay here, but McAvoy's last deal was market value. He basically signed the same deal as Werenski a week later, except the cap hit was $100k less per year, but the final year's salary was $300k more, which at the time dictated the qualifying offer.
Maybe you can convince him that Werenski's deal happened because Columbus had to bribe him to stay, but McAvoy's also been the better player, so he could absolutely argue he should get more. Sweeney should really be working to get that deal signed now because it's only going to go up the longer he waits.