I don’t think that’s true. The reality is players are stupidly loyal to their agents and can’t see that they’re essentially being used. Take Yaya’s agent, the guy is an utter moron and is responsible for not only making him look like an utter tit, but has torpedoed the last 2-3 years of his career. Others will manipulate to steer players in a certain direction. Of course, some agents are superb at their job and are probably worth the it, but many others are not.
The agents are smart too, they pick and choose their targets. Raiola supposedly made sure United paid all the agents fees for the Sanchez-Mikhi swap deal because he knew he’d get peanuts out of us. So while deals can get held up, ultimately the agents always end up getting paid and the player gets his move.