The p.golem has banefire aura (which makes him a quite decent SC imho) - and I don't really remember why the hell did I ask that question, seems unappropriate (not to say stupid) to me too. Did I really ask that?
P.S. ok, I got it. In my last big game the vetriol was added by the patch when I was at the end already. I just gave a fast look at it and it seemed to me the same cost of the poison golem (which I was using intensively) - my mistake ^_^