Yeah, but if you're (say) Lamar Jackson, you can't go and play for the London Monarchs in the European American Football league for more money than Baltimore are offering. There's in reality only one NFL and it's awash with money. As soon as any salary cap came in in football there'd be a (rogue?) association who'd pay more. Why play in England with its 100k a week salary cap, when Barcelona will pay you 200k? It happened in the early fifties when wages were capped - Colombia's league seceded from FIFA and started offering unheard of money to stars like Di Stefano because they didn't have to follow the rules. The only thing that will cap salaries is an economic downturn (!) which will simply mean that clubs can't pay out as much money. But I don't understand the economics of football, where you can apparently lose money every second yet pay idiots like Rudy Gestede and his agent £30k a week.