In the 2013 Forbes list of the richest clubs Real Madrid come top, how that is worked out I don't know.
If Spurs are insisting on such a massive fee if Real Madrid don't buy him I can't see anybody else paying anywhere near that amount.
This information comes from various sources online, All sources used quote they are for 2011/12 tax year. Real Madrids accounts are pubically available.
Richest club is based on more than cash in the bank including assets, player value etc.
Real Madrid have 590m Euros of debt.They have 841m Euros of assets. Therefore they have a net assets of 251m euros. These asset figures do not include the value of players, their estimated player value for 2011/12 season was 539m Euros. Their annual revenue is 480m Euros
Madrids cash flow over debt ratio comes in at 26%, much better than the others: Manchester United 14%, Arsenal 13% and Barcelona 11%. Simply put, the higher the percentage, the better the clubs ability to pay its debt.