Marner got 13.38% last time. He should be a fair bit lower than that on his next deal since he has now been appeased from Lou ripping him off on his ELC, and if he is serious about winning, he won't get any kind of raise (since I doubt he takes a pay cut). Matthews got 14.64% for 5 years. It would have been 16% or whereabouts for 8 years.
Let's run on an assumption that we are negotiating on an 85 mill cap. Matthews would get 13.6 mill on an 8 year deal if he gets 16%; so 2 mill raise. Marner gets almost 13% if he doesn't take a raise which is already more than fair for him. Let's say 8.25 mill for Nylander since the cap will be a little bit higher when he signs than when Fiala signed (although that number could easily go higher if Nylander keeps putting up PPG seasons).
That does not even take into account any kind of discount those guys would be willing to take to improve our competitive odds, considering the top players of other teams have pretty much all routinely done so (assuming they were paid fairly on their first deals), and our GM is not exactly rushing out to overpay mediocre depth guys with their money like many others are. The percentages above is market value for 8 year deals (they would obviously be higher for 7 year deals on the open market, but they also get less money).