There is zero chance that the Leafs' could have got Matthews for 10 (Eichel got 10 two years prior and Matthews had a ridiculously better ELC than Eichel) and probably no chance they could have got Marner for 9 either.
The Leafs' had no leverage with Matthews (who hates Babcock and who would have signed an OS - Bettman's wet dream would be Matthews going to Arizona as the first home grown star from the state and the team had been acquired by a new billionaire owner months before Matthews would have become an RFA) and not a ton of leverage with Marner (who had some long-standing grievances - some very legit, and some not so - against the Leafs' management and coach - Marner was refused the schedule B bonuses that every player drafted in his position gets, and Marner, like Nylander, was often bumped down the lineup - including to the fourth line whenever he did anything that displeased Babcock, while veteran players could play terrible for weeks at a time without facing any consequences).
The Leafs' overpayments and contract problems are actually a good cautionary tale of what happens when you draft high end talent and then are pricks to that high end talent during their ELCs. This was something I talked about frequently over the last two summers and was a major reason why I believe the Leafs moved from Lou to Dubas when they did - in the hope that it would reduce the animosity from the camps of all three young players towards Lou and the Leafs' organization. I think that if the Leafs' had fired Babcock would have been able to get Matthews for a better deal than they did (there was still more than 4 years on Babcock's contract when Matthews signed - if you think Matthews was going to give the Leafs' a discount to play the rest of the best years of his career for a coach he hates I think you live in a fantasy land - although at the time much of the fanbase was still denying that the obvious animosity even existed), but Marner's camp was out for blood - and they made clear that the Leafs' were going to pay for his past mistreatment including compensation for those denied schedule B bonuses.