You're splitting hairs between who is considered the TM client: venue or performer. Of course there may be any number of organizations between you the ticket buyer and the actual person singing and dancing onstage (venue, promoter, manager, record label, etc.).
Regardless of which of these is getting the biggest cut of the "fees", the reality is that in most cases the "fees" are line items used to increase revenue without raising ticket face prices, and TM is not the primary beneficiary.
As someone who works in the industry (but not Ticketmaster) and has spoken frequently to higher ups at TM, people should realize that the majority of the time "handling charges" are a way for performers to generate more revenue from sales while deflecting the bad PR to Ticketmaster. That's one of the services TM provides to their clients (performers/venues).
If you're a performer and you want to sell tickets for a face value of "$50", but generate revenue at the $60 or $65/ticket range, you add on some fees and let TM take the hit from the fans for "gouging" them. It's very common.
Regardless of which of these is getting the biggest cut of the "fees", the reality is that in most cases the "fees" are line items used to increase revenue without raising ticket face prices, and TM is not the primary beneficiary.