I made this post just for the sake of seeing different fish. Not necessarily for my tank. I made it for the sense that it was vague, as I am interested in seeing all types, as opposed to what will just work for my tank. So I don't care what size fish, color, rarity, tank sizes, and conditions. Just post names or pictures of freshwater fish you like and think other posters/lurkers might like.
I wouldn't be careless to put fish into a tank that wouldn't be suitable for it. Btw i can tell you obviously care about fish a lot and are passionate about them as well. You deserve a thumbs up for your concerns.
zebra plecos are really beautiful in photographs, but when properly housed are not that visible in a tank. Discus are beautiful, but not really what I consider an uber expensive fish in teh grand scheme of things.
I guess more important would be tank size, level of husbandry, etc
Personally I love freshwater stingrays. You can get some cheaper $75-$100 which are Florida stingrays, also known as teacup stingrays which do not grow as big. But Motoro stingrays are more beautiful, with great patterns, but will cost hundreds.
Like others have pointed out, Aquabid would be great site for you to check out rares, and prices. If you ever try to keep anything rare, make sure your setup is pristine for the perfect conditions needed for that species of fish.
Great question to see desired fish from all of us.
The worst defeat in the world, is when you give up.