Interesting topic. You are talking about two totally different systems that evolved differently. I would love to see a salary cap in the EPL. Guaranteed Manchester United would get relegated because a cap puts a premium on good management. In Europe the wealthy teams can just keep throwing money at their problems while the weaker teams have a much smaller margin for error.
I follow Leicester in England. They've now been relegated twice since their miraculous EPL title in 2016 - the main reason being they had to be perfect with their roster managment and they weren't. It's ironic to me that on a continent where socialism is a thing, football is, for the most part, pure capitalism. The rich compete for titles, the middle tries to stay in the league, maybe compete for a domestic cup or sneak into the Champions or Europa league if the top clubs all falter and the poor just hope to stay in the top league as long as possible. There is a heirarchy. If the lower teams develop a good player, a rich club will come for them, offer more money, pay a transfer fee and that's it. For a lower club to compete for a title you really need the stars to align as they did for Leicester in 15-16 and that just doesn't happen very often. And when it does, all the good players depart for bigger clubs shortly thereafter.
In American sports they take a wider view. Its about the product of the league. Competition is what sells. The NBA is now set up to give all teams a chance to win a title (which just happened with OKC). And with this new collective bargaining agreement the NBA is operating under - your window to win lasts about 3 years - then you have to retool as the Celtics unfortunately are forced to do now. But fans of teams 1-30 can all realistically dream of winning a title.
As far as treatment of players go - the NBA has a strong players union and everyone's making money. So they've negotiated a fairer system for players than what's happening in Europe. As far as what Ajax is doing, your TD is acting that way because he can. If Stevens were to do that, Boston would have a tougher time attracting free agent players because there are 29 other teams where a player can make similar money.
I'm guessing none of the Ajax players you've listed are super stars. So what are their options? Mid to lower table clubs most likely and probably not in the wealthier leagues like England, Spain and Germany. And as an Ajax fan, how did you feel when they sold off that roster that made a run through the Champions League a few years back? That team had some studs - most of whom Ajax wound up selling prior to the next season.
I like the American system better only because it gives everyone a chance. I just can't see getting excited about a season when realistically only 2 or 3 clubs have a chance of winning a title (maybe add a club or 2 for the EPL). The Euro system also provides a cushion for lousy management or ownership - both of which are just not tolerated in most US markets.