Aquitori,
Kingkong and Valarc have given excellent definitions.
But....."High End Hobbyist" on what scale?
In Kentucky, a person that has what could be classified as a koi pond....a few thousand gallons, deep, some decent filtration and some koi you could point to and call by 3 or 4 of the variety names we know,
that person would be called a 'High End Hobbyist'
here compared to the thousands of other people in the state that have a pond at their home. You would probably call them a newbie.
In Kentucky, what you and Kingkong and Valarc and others on Koi Bito would call a 'High End Hobbyist' would be called a 'Fish Idiot' here!
Dale