I can't speak for the Clones since I don't own one, but I do have the Fleet Trooper whose helmet is a rigid plastic. It's a higher quality material (just knowing how that type of plastic costs, compared to say poly-vinyl like SW figures are made otu of now for the most part). If the Clone armor is the same rigid plastic, it's definitely a quality product... I can see the price being up there, regardless, if that's the case.
Again though I don't own a Clone to know.
$120 though seems not too bad, plus isn't some of the gear new on a guy like Gree? Or other guys getting a new helmet, or whatnot? Again I could be wrong.
Just seems like what you get is insanely worth the price to me. I don't have the money to buy (right now), but wholely intend on playing catch up over time.