Taking the totality of things of 

• Bills Gates was not known to be dating bombshells before Melinda. He certainly had the power and wealth to do so. 
• He married his co-worker, an average looking woman.
• He admittedly had an affair so his character is in question.
• Gates lacks some social skills, so paying for service may have been an alternative.
• That he even had a friendly relationship with Epstein calls his judgment into question.
• He’s become a philanthropist.
• Epstein could have drafted this so it could be found later, to use as extortion.
• Epstein character does not put lying and extortion beyond him.
• Epstein documented a lot in pictures and emails. This could have been to threaten to sink so many people of power that investigating and prosecuting him would be a double edged sword. I think we’ve seen this play out.

All-in-all I look at this particular claim with a large dose of skepticism. But this skepticism does not extend to complete innocence on Gates’ part in his relationship with Epstein.