Football's rich list - the hidden story

The publication of Deloitte's football rich list confirms the status of clubs such as Real Madrid and Manchester United as being amongst the sporting world's top revenue generators. However, what is the relationship between these clubs' revenue streams and their debt levels, player transfer fees and salary costs, and the economic downturn? Moreover, if a club signs a player like Cristiano Ronaldo, incurring massive costs in the process, is their presence in a team likely to be sufficient enough to generate revenues that will offset these costs? (Does it need to?) And how would this be reflected in football rich lists?