Isaiah Thomas was looking forward to this summer. One year ago, he dreamed of signing a five-year contract that would pay him almost $180 million, including more in the first season than he’d banked in his entire NBA career. Instead he signed a one-year, $2.1 million deal—the least amount of money any team could pay him. He went from a maximum contract to a minimum contract.

He’s an extreme but unfortunate example of the curious economy in today’s NBA.

The...