The Belgium international has impressed since moving to Villa Park from Genk for £8m last summer and the club are reportedly keen to extend the player's deal.
Tottenham Hotspur have reportedly been linked with a move for Benteke, but Lambert has revealed that he has no plans to sell the frontman in the summer transfer window.
He told BBC Sport: "He is hot property. If you wanted to prise Christian away from here you would want a sizeable cheque, that is for sure.
"He has the potential to be fantastic. If you look at modern day figures then £25m is probably a good start.
"We can't stop people looking at him but he is under contract here. He is enjoying his football at the moment and doing fantastically well."
Benteke has scored 15 goals in 29 Premier League appearances for Villa this season.