You're right -- LeBron has a dramatically larger impact on the game than Jon Lester, which is why his wins above replacement is dramatically higher. And that's also why it's kind of crazy that John Lester gets a higher salary than LeBron, which is what I was pointing out.
It's a different game with different matters of importance and salaries.
You also have to factor the caps. In baseball you don't reach the Luxury Tax until you spend $189M. The salary cap in basketball is about $63-65M (I think). f basketball had a similar cap, Lebron could be at $75M.
Everything about these sports are different, Trying to make any linear comparison is foolhardy.