The problem is that at one time, 57% was a good number to allow for the players. When that number was negotiated, it didn't cost nearly as much to operate an NBA franchise as it does now. Unfortunately, all the non player related costs have gone up and there is no cba to keep those numbers in check.
For example, the cost of staying at hotels has gone up as has jet fuel, coach salaries, advertising costs, cost of living for the 100 or so employees that work for NBA franchises and so on. When the cba was negotiated, the owners could cover the remaining 43% with non player costs but now, it appears as though the number has exceeded 43% and coupled with the player's getting 57%, you get red ink.
That being said, I think the owners are full of it when they claim those massive losses. As a whole, the league turns a profit IMO but the fact of the matter is that while the big markets will always profit, we have gotten to a point where the small markets aren't profitable and in order to stop that from happening, player salaries have to be cut back.
Remember, the owners can't just tell the hotels, oil companies and billboard operators to charge less. Those costs will always go up and up. As a result, they can only get money back from the players via collective bargaining. Here's hoping that they can meet halfway.