Officials at St James' Park have been desperate to keep a lid on the fact that the striker, who has netted 15 times this season, is available for the right fee.
But asked about a £10m release clause, Spurs boss Harry Redknapp said: "I think you will find it is a lot less than that."
Asked if was as little as £7m, Redknapp added: "Even less than that."
A whole host of clubs are set to investigate poaching the predator who destroyed Manchester United last week with an outstanding display.
Liverpool, Sunderland, Everton and QPR are all in the hunt for reinforcements up front. Ba left West Ham last summer as he had a clause in his contract saying he could quit if they were relegated, says the Mirror.