I can't see how a salary cap would be introduced officially. It would take only one player to go to the European Court of Human Rights (similar to what Bosman did) claiming restraint of trade.
Players with smart agents could screw the whole system. Try this one. Remember how Hollywood tied actors to 7 year contracts years ago, so that the actors had no choice in the movies they worked on and couldn't work for other companies unless they had permission. Now they are free agents. They freelance and choose which films they want to work on or audition for. So why shouldn't they hire themselves out to the highest bidders on one year contracts. Do you think Real Madrid, AC Milan, etc will really ignore the top players and sign cheaper, less talented players? Of course not.
What about clubs like Juventus? They may agree in principle to a salary cap but what if, as an example, they agree to only pay Trezeguet £50,000 a week, but FIAT which bankrolls the club also pay him £50,000 a week? Legally you can't do anything about it, if FIAT says he is also employed by them to do PR work.
Like anything else, certain clubs will bend the rules.
They would need to be part of an organisation that had some way of regulating this, so that if you were found guilty of violating the agreement, you could be suspended from the competition for, say three years.
Possibly the best thing would be if the clubs had an informal agreement not to spend huge amounts on wages which would be in their own best interests, so that they couldn't be held to ransom by players.
With regard to ticket prices.....they will never come down, unless the actual attendances drop so far that clubs are desperate to attract crowds.