Interestingly, an economist recently estimated LeBron James' fair market value at 50 million dollars a year, which is far above his 20m current salary (which is largely driven by the CBA to keep player salaries low).
Also, when you sign an NBA contract, most of it is guaranteed both ways. That is to say, a four year contract means you get paid for four years even if you get injured or your performance is lacking. The converse being, you can't simply sign with another team for higher salary if you feel you're being underpaid, underutilized, or under appreciated. There are exceptions, player and team options, but those are typically in the final year of a multi-year contract.
I don't have strong thoughts on the general point of the article, but I thought I'd clarify some of the basketball background info, because I feel it's somewhat misleadingly presented. And I'm not sure the NBA really serves as a great analogy with the author's points.