Clearly it had nothing to do with the Indians since they were using smoke signals. And I don't think caveman really cared.
Maybe Mozart was responsible but I think he was deaf.
Didn't Thomas Edison invent the turntable so maybe he should get all the credit.
I do not think you can assign a dollar limit to when hi-fi begins. If you did it would have to be above $2500 since you can't discern Quality music below this level.
This is a difficult question.