that's one way to look at it but it sure is slanted
when talking about Nurkic as a C compared to other NBA C's, he isn't worth 18M/year even when healthy; he has negative value. It's probably not significant negative value, but it's pretty damn easy to gauge compared to the rest of the NBA
but that's assuming good health...which Nurk doesn't have. He's been in the NBA for 9 seasons and has averaged playing in 51 games while missing 29 (Covid adjustment). He's missed 36% of his team's games. Now, some of that is due to tanking so you have to adjust downward a bit. Still. And over the last 4 seasons, he's played in 153 games while missing 157. Worse is that in his time in Portland the Blazers have played 35 playoff games and Nurk has missed 19. He isn't there when needed most; although the 'need' is debatable since the Blazers actually had some playoff success with Kanter at C. They lost every series when Nurkic played because traditional C's have diminished roles in the playoffs
gauging player value resides in some foundational factors: talent-versatility-impact-consistency AND availability. Nurk has some talent and he has some regular season impact. Not so much in the playoffs. But he's not versatile or consistent, and his availability is poor. Negative value
the debate has devolved to the point where the biggest remaining argument for Nurkic is simply that Portland doesn't have anybody better. That's a poor argument in his favor, especially for a team in a major rebuild when wins don't matter and with a coach that schemes defense opposite of Nurk's abilities
