Maja completed a switch to Bordeaux in the winter transfer window for an initial fee of £1.5million, although that amount will rise should the youngster continue to excel.
And French publication L'Equipe has now revealed details of his salary at Nouveau Stade de Bordeaux.
They claim that Maja is earning €65,000 a month at Bordeaux, which equates to roughly £56,000.
His new salary is in stark contrast to his previous wage at the Stadium of Light - with owner Stewart Donald confirming the youngster was on a contract worth under £1,000 a week.
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Speaking to the Roker Rapport podcast, the Black Cats' chief stressed an urge to improve future contracts to ensure that youngsters like Maja weren't left on salaries that undervalued their contribution to the club.
He said: ““It’s cost us by not having it organised correctly.
“You can argue I should have started that (negotiation) in August instead of end of September but to be fair when I came to the club, Josh Maja wasn’t particularly well known
“Every week we were trying to organise a contract, he scored another goal. It was the perfect storm.
"What we should have done is turned around and said when he starts playing, the boy was on less than £1,000 a week, you start earning more money but we get more years.
“We might be in the same boat with Benji (Kimpioka), who is in the last year of his contract next season, doing it after the event, the price just goes through the roof."