Song played on loan for the Hammers from Spanish and European champions Barcelona during the 2014-15 season.
The former Cameroon international midfielder gave a good account of himself on his return to the Premier League.
The 27-year-old created 28 chances in as many league appearances, and had a pass accuracy of 76%.
Song won 17 headers, 39 dribbles and 73 tackles in those 28 Premier League games.
It has now been reported by The Daily Star that West Ham have been told that they will have to cough up as much as £10m in transfer fee if they want to secure the services of the former Arsenal midfielder.
Based on Song’s overall performances over the course of the 2014-15 season, £10m for him is not too much.
Although the Cameroonian’s form dipped in the second half of the season, he was superb in defensive midfield in the opening months.
West Ham will have to replace Song if they do not sign him on a permanent deal, and better options will cost more than £10m.