Federer had not planned on playing at the Italian Open this week as he wanted to rest ahead of Roland Garros.
However, the Swiss star’s Madrid Open campaign was cut short with a quarter-final defeat to Dominic Thiem.
He then decided to take up the opportunity to get more practice on the red dirt.
And the Italian Open responded by doubling the prices of tickets from around €60 (£52) to €132 (£114) for Wednesday.
A statement was released by the Italian Tennis Federation which read: “We have doubled the price of tickets for Wednesday, the day Federer will play.
“We want to reward fans who had bought tickets before they knew Federer would play.”
Supporters have hit back at the Italian Open.
“Yeah, I’m a fan who’s going on Tuesday, but would’ve bought a ticket now for Wednesday also, just because of Fed,” one fan wrote on Twitter.
“Now I can’t afford one, so I’ll skip. Great move.”
And another user added: “Omg this is not fair!”
While a further fan commented: “The other way to look at is PRICE GOUGING! That is wrong!
“Shame on @InteBNLdItalia #ATPRome #IBI19.”
One person wrote: “Is this serious! I’ve never heard of that before. Surely they Can’t do that?”
And he was backed up with: “Thats an awful decision and approach.”
Federer will face the winner of Frances Tiafoe vs Joao Sousa in his opening match in Rome.