Redknapp claimed last week that the striker would be able to leave the Sports Direct Arena at the right price.
Magpies boss Alan Pardew later criticised his counterpart for talking about the Senegal international.
However, when asked if the clause was £10m, Redknapp told reporters: "I think you will find it is a lot less than that."
Asked if the price was in fact £7m, the 64-year-old said: "Even less than that."
Ba, who has scored 15 goals this season, is currently on duty at the Africa Cup of Nations.