To evaluate a players value, I like to compare with previous trades involving similar players (position, age, pedigree).
Two trades involving forwards in their mid 20's, comparable to Necas, come to mind: Schenn and O'Reilly trades to St Louis.
O'Reilly: Thompson (former late 1st) + late first (#31) + salaries (Sobotka + Berglund = 7,350 mil) + 2nd Rd pick
Schenn: Jori Lehtera (4,7 mil) + late 1st in the trade year (2017 27th) + conditional 1st pick of next year (top 10 protected: 2018 14th)
As I said in a previous message, the goal for Carolina in trading Necas is to save on his contract and stay competitive at the same time.
So want it or not, they're gonna have to sacrifice somewhere as no team are gonna give them an equivalent talent that make less money.
They'll have to take a risk somewhere...
Both those guys are/were very different players to Necas though.
For one they both were established young-ish centers at the time of their trades as opposed to Necas being a pretty clear winger (as horrible faceoffs numbers, deployment, and his weak defensive game when played at center indicate).
To add, there's also the fact that the players in both trades you mentioned were quite a bit stronger defensively than Necas is (a LOT better in O'Reilly's case), simply more physical players, and the comparison starts getting a lot murkier.
I'd argue that 2 comparion points that are more apt to use for a Martin Necas trade would be the DeBrincat trade from Ottawa to Detroit, and the Sam Reinhart trade from Buffalo to Florida.
Reinhart returned a very good goalie prospect in Levi + a protected first in a later draft in the 2021 offseason.
DeBrincat returned Kubalik, Sebrango, a fourth-round pick in 2024, and a conditional first-round pick in 2024 that ended up being the 25th overall in this year's draft.