Villa signed Benteke from Genk on the final day of the summer transfer window and the 22-year-old has more than justified the faith shown in him by Lambert. He has netted eight times and the Barclays Premier League's record goalscorer, Alan Shearer, claimed his performance at Liverpool last weekend was the best he had seen by a centre-forward this season.
Now Benteke will be looking to continue that form in Sunday's clash at Chelsea as Villa strive to extend their unbeaten league run to six games. Lambert said: "I think Christian, since he came here, has been excellent. He was probably unheard of and nobody really knew too much about him."
He added: "Then all of a sudden he's doing what he's doing and then everybody takes notice. He's been an absolute steal, for what he's doing and the way he's performing.
"The way the modern transfer market is, it's incredible the way transfer fees are. The inflation of it, and transfer values, are ridiculous, but I'm pretty sure he's not worth £7-8million now!
"Is he priceless? I don't look at it that way, I just know what he's doing for the football club and what he's doing for himself and his team-mates.
"I can't speak highly enough of what he's done."
Lambert expects Benteke to cope if he becomes a marked man with opposing sides after his eye-catching performances.
He said: "Christian might well be a marked man. If he is, then it's a compliment to himself and it's something that he'll have to combat if that's the case.
"But he will because he seems to be a lad whose got a lot of confidence in himself to perform, not in an arrogant way at all, but I think he's got good belief about his ability."