Hi-Fi is a unit less concept. It can't be turned into numbers, so there is no official, measurable definition
If you define "Hi-Fi" as "The amount of money you have to spend get sound quality that is acceptable", I think its different for different groups of people.
OCN: $200 and up
Me: $3.000 and up
Audiogon: $20,000 and up
Ascend Sierra-2, Sierra RAAL towers, Salk RAAL Songtowers, Kef LS50, Revel Performa 3 M106 are examples of a few products under $3,000, would you consider them hifi, or is the price tag what defines hifi for you?