Let’s looks like fun. I’ll take a shot at it:
Low-Fi:
"Perceived value" driven with emphasis on features and/or convenience. Provides minimal performance with just enough "information" tossed out in the space for listeners to recognize the basic elements of the performance or, in the case of "home theater", deliver decernable dialog -- if you have excellent hearing. Wide distribution enables economies of scale and manufacturing efficiencies making the item competitive with other "like" products. Zero consideration for service/support in that repairing the item would cost more than producing (and, shipping) a replacement. Sonic attributes include: one note bass, "pinched" midrange (fundmentals are anemic), sound coming from 2 channels but not a "stereo presentation" as we understand it. Unable to answer the bell when dynamic passages require it.
Mid-Fi:
Legitimate attempt to provide some level of audio performance, given budget constraints. Often teathered to "brand recognition" where some familiarity of the manufacturer is desired. "Nitch" pieces and obsure brands often do not play well in this space but can be successful if they perform well above their weight class and are good at making themselves visible in the marketplace. Features and convenience are usually strong considerations here in that "mid-fi" users are not programmed (yet) to abandon the "cool stuff" on the front panel or remote control. Some level of service and support exists, often with good-to-excellent communication with needed resources. Audio attributes would include the ability to provide a strongly emotional experience with mimimal listening fatique. Some "warts" in the sonics are acceptible and given a "pass" due to cost of the equipment. Parts and build quality are limiting factors to "affordable" price ranges, while relatively high volume provides good manufacturing efficiencies and access to new (and, often expensive) technology amortized over many units. Good-to-excellent "bang for the buck" is a common attribute in better examples of the "mid-fi" price/performance range. There are rare instances where ’mid-fi" priced gear can be a world beater, and history has demonstrated that this over many decades. Yet, other examples of "mid-fi" priced products, regrettably, have Lo-fi performance (or, worse).
Hi-Fi:
The differentiation between Hi-Fi and "high end" is a subtle, but important one. It has also been said that "high ticket" is neither "Hi-Fi" or "high end" because it could ungloriously fail to satisfy the goals of each.
Hi-fi asserts a loyalty to the original. In those "suspension of disbelief" moments, we are emotionally and intellectually transported to another place -- temporarility suspending our belief that we are engaged with a substitute for that reality -- a mere facsimile, and not the "thing" itself. The "price of admission" can be rather daunting. The level of precision required, robustness of parts, manufacturing inefficiencies, and engineering costs spread over a relatively small number of units can reach the sky pretty rapidly. However, as mentioned above, all the stars CAN line up and a product can be greater than the sum of its (humble) parts.
Reaching the highest plateus of audio performance is often accompanied by a high degree of attention to esthetics, a impressive credibility story attached to uncommon attention to details -- or both. Exceeding the price point of affordablity above mere mortals does provide a level of prestige and exclusivity to the brand. The assumption here, of course, is that many dollars spent will pay sonic dividends and, a wild degree of emotional attachment to the esteemed brand.
Hi-fi is not necessary a "this AND this" proposition but rather a "this OR this" proposition. Performance CAN be the strongest consideration and delivered in full glory with a very strong cost/performance relationship. So, obtaining stellar SQ with a minimalist approach is still "Hi-fi". And, yes, beautiful pieces with stunning great looks can sound spectatular as well. They’re just going to cost (much) more.
Each listener will determine what "exit" they want to get off on. Hi-fi to some may be Mid-fi to others. The term "intelligent ignorance" comes to mind here. Not knowing what you "don’t know" can be a blessing. And, save you a lot of money.