Sunderland owner Stewart Donald reportedly wants a total of £90m for the club.
The Black Cats are playing in League One at the moment and are aiming to clinch automatic promotion to the Championship at the end of the season.
The Sun has claimed that Stewart values Sunderland at £50m, but he wants £15m if the team get back to the Championship and a further £25m if promotion to the Premier League is achieved.
USA-based MSD Partners want to buy Sunderland, but they do not want to pay what Stewart is demanding, according to the British tabloid.
Search for a new manager
Meanwhile, Sunderland remain on the hunt for a new manager following the recent departure of Jack Ross.
Ross failed to guide the Black Cats to promotion from League One at the end of the season, and results so far this season have been underwhelming.
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