Seems like Detroit got a bad deal on Larkin there. Guess Larkin did not want to commit to his hometown team if they did not have much of a future. They should have been able to get that number on a 7 or 8 year deal, similar to what Nylander should be getting.
I still think 8 x 6.25 AAV is what Nylander should be getting. Detroit should have got more term out of Larkin in the first place, and there are a few things to also consider.
1) Larkin is the guy in Detroit, so he's going to get a better deal just off of that. Nylander, at best, is number 3 behind Matthews and Marner.
2) Larkin is getting valued as a full time center right now. With Tavares coming in, Nylander is nothing more than a part time center from now on. That is something going in Larkin's favour.
3) Similar to number 1), Larkin had very little in terms of offensive support. Larkin was the top scorer and did not have much in terms of high end talent to help him. Zetterberg and Mantha are pretty much it last year, but both would be in the JvR/Marleau category, which would put them behind Matthews, Marner, Kadri and Nylander (as well as Tavares, but he was not here ast year) in terms of what the Leafs had. Not only does the lack of offensive support not help, but teams would stack up against Larkin. Teams would stack up against the Matthews/Nylander line too, but it's a lot tougher given the Leafs' offensive depth.
4) Larkin put up better production last year. He had similar PP time as well.
The main counterpoints are that Nylander has had two very good seasons now (although once again, both playing with a lot more talent than Larkin got) and that he was able to put up similar production in a lot less ES playing time. I am not going to comment on defensive abilities because I doubt either really have a major leg up on the other in that area besides maybe the position they play. It seems like both are solid but unspectacular in their own zone.