And that's why every open league has salary cap around the world.
Remind me on which of them is the league competitive, and how many different champions each league had (comparing to the NBA).
Remind me which league is by far the best league around the world?
Remind me on which league this game is based upon (12 minutes per quarter, 6 fouls per player, etc.)?
Remind us all, why you did not answer a simple question, why it will not work on this game.
With an explanation.
If I follow your last argument, every division should have a salary cap of 300.000 (number thrown out of nowhere yes but you didn't make that far into a concrete suggestion, I had to). So, 300.000 for D4, 320.000 for D3, 340.000 for D2, 360.000 for D1 ?
Each division on each league will have its salary-cap and luxury-tax based on the league's value (AKA average salaries around the league).
By that there will be some differences between teams, but they will be limited to keep competitiveness that will be based on other BB-managing skills.