The "Must haves" and "Specifics" are much more common the more expensive or exotic you get, just part of the trade

. I get an ear full from a couple pleco mad mates about were I buy my plecos from even. Some who willing spend 250+ on plecos

. But I can tell you for sure the more you get into discus the more you'll be hearing about the specifics. To most who have discus they are happy with good fish. But the real serious discus addicts have very sharp eyes especially shape or other minute details that you and me probably wouldn't even notice
Actually on the expensive note I was working in the Water Quality Lab at the aquarium near me today and was told to check water for Seadragon exhibit in which they were getting ready to add 2 10,000 dollar seadragons. Hope I didn't mess it up