Current market would be the obvious comparison for salary, while Athletic and other hypotheticals are nice, there is known high and low salaries currently and those are the teams Toronto faces.
With that said, I do think Marner has produced at the level needed in regular season, its just a shame his ability to elevate hasnt carried through to playoff production often enough. It also feels like hes been involved in an abnormally high number of key playoff mistakes. The turnover on the GWG in game which basically ended our series/season followed by his overall play in game 3 in FLA. The TB turnover and inability to stop a zone entry for the GWG in game 6. The misplayed coverage on TB's G7 Winner after Muzzin gets hauled down. The G7 turnover v. MTL, the over the glass v. Mtl in G6.
That does ignore the good, like his overall play in both TB series, the GWG v. Fla in Game 4, his Game 5 "shot pass" v. TB.
But really you want to clean up those crucial mistakes by him and to a lesser extent Matthews in playoffs.