I especially remember one particular feature that was really useful and really easy to enable in Enterprise Manager, but that would cost you at least $10000 at next license review (probably more if you had licensed it for more cores etc).
What I wrote about above wasn't us changing something or using a new feature but some sales guy at their side re-interpreting what our existing agreement meant. (I was not in the discussions, I just happened to work with the guys who dealt with it and it is a long time ago so I cannot be more specific.)