Contraction.
Furthermore, the more you tinker with artificial restraints, the more you increase both the complexity and number of unintended consequences. The NHL didn't adopt the idea of a cap+linkage because they knew they'd lose money by going to a 54-57% range. They probably believed at that time that that was a very acceptable range ~because~ they had cost certainty.
The certainty overlooked was that it certainly would cost something, and that 'something' wasn't necessarily a good thing for everyone. (Which actually was predictable as I keep reminding you.)
Also, in attempting then to make a cap manageable from a roster building perspective, they had to throw in things like variance and buyout formulas, the salary averaging, bonus considerations and lack of bonuses as an option, and so on.
Each step you take in one direction potentially makes it difficult to do something unintended in another direction that may be beneficial or mitigating of your risks. This all speaks to why letting markets function as efficiently as possible because you then can react to actual conditions, not be shackled into something that removes your ability to maneuver.
That's really one beef I have with salary caps. The GMs' toolbox is quickly being depleted of options that actually help them control costs and any ingenuity they can bring to the table.
I dislike that player movement is stymied because I believe that's actually good for teams and fans, and maybe even players. Instead of having this based on 'hockey' decisions, they're cap decisions now.
And yes, free market and such. The leagues try to create an artificial market on player salaries because they want to ignore the real market they cannot control--- the economics of the real world in which the franchises must operate. When fans don't show up in buildings, and no one pays for a TV contract, or there's a lack of sponsorship, etc., this is the real market speaking to them. It has made a choice, and the choice is --- we're not going to go to your games at all, or certainly not going to pay $60. (Refer to the footprint argument below as well.)
Their answer is to try to lower what all players earn to make the team that can garner $25/ticket viable. Please consider what you pay for a college football ticket to gauge how low that actually is, and if you think the owner who has that team is in the right business (pro sports).
Of course, you will come back with the national footprint argument and the massive TV contract, and I will remind you that it's set for the next 10+ years and the current batch of owners will have cashed out by then.
There isn't an example anywhere in the world that shows market manipulation and restraints can escape real market conditions. It's not a hypothesis or choice (that market principles exist), it's a demonstrable fact by simply starting with supply and demand for anything that's for sale anywhere in the world.