Benteke has scored 14 goals since his £8 million arrival from Genk and has been linked with Arsenal, Chelsea and Manchester United. Lambert is understandably eager to keep the Belgium international at Villa Park, and warned that potential suitors would need to dig deep to prise him away in the summer.
"When the guy came into Villa, people were saying to me 'who is he and why are you going for someone from Genk?'" Lambert said.
He added: "With what he's done, he's a cult hero already. He's only 22 and he's got years and years ahead of him. He's not at his peak, but what he's done for me and for the club is fantastic.
"If someone wanted to buy Christian, they'd better have a few quid in their pocket."
Asked whether Benteke's performances have doubled his value since last summer, Lambert replied: "Yes, by miles.
"He's not just going to walk out of here for the value he came for, that's for sure.
"We have given him the opportunity to show what he can do and I think he is loving his football at the moment."
Regarding the rumours that Benteke wants to leave Villa, Lambert said: "If that's the whispers coming back then it's funny that because he doesn't speak!
"I've not heard it. He's a cracking big guy and really humble. If he keeps that, he could be anything he wants to be."