Salary cap, luxury tax and aprons: why can't the richest NBA team buy everyone?

Unlike European football, spending in the NBA is limited not primarily by a club's revenue but by a central set of rules that applies equally to everyone.

The salary cap

The league sets an annual figure that a team may spend on its players. It moves with league revenue, so as income grows, so does the cap. The system is "soft": exceptions allow teams to exceed it, for example when re-signing their own players.

The luxury tax

Teams that go beyond the threshold pay a penalty tax to the league, and it is progressive: the larger the overage and the more consecutive years it lasts, the more expensive it becomes. Part of the money collected is distributed among teams that stay below the line.

The apron levels

The most recent collective bargaining agreement introduced two further thresholds. Above them operating costs are not merely higher: the team loses its most important roster-building tools, finds trades harder, cannot use certain exceptions and is restricted in how it can use future draft picks.

Why is this good for fans?

Because the aim is competitive balance: nobody can buy every star at once. That is why great team-building projects break up after a few years, and why a champion is sometimes forced to let a key player go the following summer.