Comparing McDavid's salary to Matthews' is unfair as their were done under different salary caps, etc. The Leafs wanted Matthews and Marner in their productive windows while they had Tavares and Reilly. Nothing really matters after that. Matthews will likely head home to Arizona (if the team is still around) or nearby to Vegas or LA.
Matthews is all about winning the big one, I think that will be the main consideration for his decision.
If the Leafs are still very competitive, Leafs have every thing he needs, relationship with the club,
love of management and fans, big stage, great diverse city, etc.
If New York or Los Angeles are trending towards a shot at the Cup, it might be a problem.