That is my point right there. The discus in my avatar is a beautiful fish. I do not care if it fits the arbitrary, made up description that someone else decided discus should be. It is a beautiful animal and that is why I hand picked it from the wholesaler. Many people have felt the same way over the years (in the shop where it was in the display tank and people on forums seeing it as my avatar) and that is why we were able to sell it for $125 at the shop. The fact that the people who liked it haven't been told to like certain traits in discus and look down on others allowed those people to enjoy that fish. I still think it is the most beautiful discus I have seen. Yes, the high end discus are also amazingly beautiful and stunning, but I am glad to say that I can still appreciate and enjoy the 'lower quality' discus that are out there.
Many if not most centralized filtration systems utilize UV sterilizers so that it is impossible for water in one tank to get to another without going through the UV. Very few pathogens can infect healthy, unstressed fish. You can expose them to pathogens all day long and they won't get sick. Stress them and no matter how sterile your procedures are they WILL come down with something.
I personally do not agree with sterilizing everything. Things have immune systems. It doesn't matter if the net was just in a tank with ich, it is not going to spread ich unless the other fish are stressed. I am not saying I would do this knowingly or suggest it, just that it is not this evil that if there is ich around fish will get it.
That markup is not accurate. I work at a local shop and ran it in the past. That may be the ideal, but depending on what type of fish it is, what we have to pay, what the demand is, etc. that can vary dramatically. We fed discus 3-4 times daily. This may not be the extreme that some breeders go to, but again they were thriving. I don't know why a shop wouldn't feed on Sunday. Perhaps you are referring to any day they happen to be closed (which may or may not be Sunday) but even then many if not most shops still have someone come in to feed. I think most local shops take better care than the homes most fish go in to. So the fact that a local shop may not match the care a breeder may provide doesn't really say anything to me. If anything these fish need to get ready for home care, which is likely not to match that of breeders.
That is the opposite if Biology. If an animal is never exposed to pathogens it doesn't develop a strong immune system. There have been studies showing that the younger children were when they started working in the barn the less likely they were to have allergies or asthma. Another study showed that children who are pampered are much less capable of handling stressful situations as adults than people who did have stress as a child. Yes, I will raise my children under the idea that it is okay to be exposed to germs and that sometimes the other team wins and you lose. I think children are a good analogy to this. Which is hardier: the yuppy kid who is pampered, is sheltered, never gets to play in the dirt, has to wash his hands after every time he touches anything, or the kid who drinks from the garden hose after exploring in the woods all morning and who does have to deal with real life let downs?