By Ali Lyon As the US Open enters its decisive week, a look at how Grand Slams generate revenue – and which one makes the most money. Like many tennis Grand Slams, this year’s US Open will be box office in more ways than one. On the court, the last Grand Slam of the year has already thrown up several salivating plot lines. Men’s world number one Jannik Sinner plays in what is his first tournament since being cleared of any wrongdoing after a positive drug test. Naomi Osaka made an emotional – and triumphant – return to the US Open, having missed last year’s tournament after pulling out of the …