In this regard, LeBron is a unique case, as his stats have barely changed over the years. Most NBA players his age are either long retired due to injuries and lack of motivation, or get the veteran minimum while sitting on the bench. Yeah, I know he spends a lot of money on his health, but motivation to keep playing basketball is also a big factor in his case.
In principle, I think he can play at least 2-3 more seasons in the same rhythm.
Add popularity on the mix as well. Without that, he will not get paid more than $40M per year.
I mean let's face it. He's one of the greatest basketball NBA players of all time, and he achieved so many things already - so many that no one can comes close to it (including the total career points).
I agree with what you said though that if it's a different player that has the same age as him, teams might give him only the veteran minimum or might not even get one. In Le-GM's case, he's as efficient as other superstars out there that's obviously younger than him, and that's what makes him unique to other players that has the same age as him. He's consistent all throughout his career especially in points. As for him playing, I guess his 2-year contract will be his final one, and after that, it's very sad to say but he might retire at that point.