I'd say somewhere in the 50's with the introduction of the Quad ESL 57's. Next thing to really rock the hifi-world was the introduction of the Philips CD100 in '81 ('82?). The Meridian remake (MCD100) showed that CD wasn't as perfect as everybody claimed it to be. Just my 2 cents though.....
The Single Piece That Started Today's HIGH END ?
I have no idea myself but it has been suggested that it may have begun in the mids 1970s, with a Mark Levinson preamp. It apparently cost more than anything anybody ever concieved a piece audio gear could cost before. It may have simply been here since the start of McIntosh (1949) which was always a more expensive and exclusive brand. What are your thoughts?