Thats a pretty poor ratio of success from 18 players but we'll just gloss over that.
Fair enough but I think, that Lambert bought some players knowing that they will improve. Helenius, Bennett, Lowton, Westwood, Luna, Tonev, Kozak, Steer and even El Ahmadi, Are you including Guzan and Bertrand in the 18?
Bowery was a long shot. Holt for experience.
If he adds two quality players each year on a shoestring he's doing alright, maybe that's just gloss for you.