Half of the fine had been suspended until the end of the 2017/18 season, the Six Nations said.
Maestri, 29, admitted that he "committed an act of misconduct and openly apologised for making the comments", the Six Nations said in a statement.
Maestri had criticised the performance of English official Barnes after the March 18 match that ended with France snatching victory following 20 minutes of added time.
France felt the game should have been brought to a close sooner with a penalty try as Wales were repeatedly penalised at the scrum.
"He (Barnes) told us we were not dominant enough," Maestri told reporters after the match.
"Anglo-Saxon referees always talk about fair play but the reality is that they think we're cheats.
"When you are repeatedly crushed in a five-metre scrum, you concede defeat. There's a complicity between Anglo Saxons and it is in these moments that you realise it. It was unbelievable."
($1 = 0.9309 euros)
(Reporting by Julien Pretot; Editing by Keith Weir)
