I'm confused as to how you think this would solve anything?
Such a high cap would only affect industries that don't have equity benefits to offer its employees. I.E. this effects the entertainment industry more than any other industry, and the talent and artist than it does managers and CEO's.
In your footballer's example you have to also consider that the footballer is looking at a career lifespan of less than ten years with only four of those years at best at top earning potential (and this would be for a star player). Not to mention the fact that most sports contracts are not guaranteed money. In the case of almost all pro athletes missed games due to injury and under-performance means less money earned on the contract's potential earnings. Other than health insurance, there are no other equity benefits. What could a team offer? Stock in a soccer team? Most of those ventures hemhorage money since they are more of a prestige investment and not a business investment. However that player who is payed a few million a year sprouts around him a multiBILLION if not TRILLION dollar industry. His skill puts fans in the seats, who buy jerseys, who eat at the restaurants nearby, who buy gas on the way, and who purchase air fare and hotel tickets to see their team out of town.
Now onto music industry. Artists typically earn their money from royalties. That is from each piece of music sold, played over the airwaves, and otherwise distributed among traditional media. This is the music industry's way of minimizing risk when involving itself with pressing and distributing an artists recording. If a new artist bombs they absorb the cost of printing some plastic, but they aren't on the hook for a failed artist's salary over the terms of a contract. Problem is nowadays a larger share of the audience is helping themselves to pirated copy's. Resulting in lost sales. Not too mention radio continues to lose its share of listenership to mix cd's and mp3 players you can imagine the upheaval at hand.
Second with the exception of the entertainment industry which deals purely in pomp, hot air, talent, and all things intangible, top flight compensation for employees a company feels are high value rarely is a disproportionate expense on a company's balance sheet. Third most executive employees are compensated in other things other than cash, such as company penthouses, cars, stock equity, health insurance, pension plans, pre paid vacations, no questions asked expense accounts, ect. A salary cap would simply lead to an increase in perks and other likely untaxed compensations, since the goal of high salaries in the first place is to attract the best and most talented out of a limited pool of exceptional individuals, not simply throw money in some black hole to never be seen again. A final point to make is that money spent on salary by a company is hardly wasted on the economy. It circulates whether an exec rolls it into an IRA where it is invested in a hedge fund who in turn invests in a small wind farm startup, or an auto parts welder who purchases some football tickets.
