The x00/x02, x04, x06, x07/x08 names does not classify the target market for the chip, but the size and/or feature set of the chip in that chip family.
Back when GTX 680 launched, it featured a GK104 chip. In the consumer GPU market back then, it was clearly a high-end product. GTX 1080 launched similarly with a GP104 chip, and it was a high-end product for a few months. What is classified as high-end, mid-range and low-end at any time depends on whatever is present in the market at that time. The product makers intended market place is irrelevant, and so is pricing. If e.g. AMD decided to price a Polaris product at $2000, it will still not be a high-end product, and no one in their right mind would call it so.
The only sensible way to segment the market is by making a scale between the highest and lowest performing product on the market, then dividing that scale into three, and grouping products accordingly. We can argue about where exactly to draw the line between mid-range and high-end, but regardless if you use a linear or slightly exponential graph, you will end up with something close to the same thing; in the current market RTX 2080 is high-end, RTX 2080 and GTX 1080 Ti is in the grey area between upper mid-range and high-end, Radeon VII, RTX 2070, RTX 2060, GTX 1660 Ti, Vega 56, Vega 64 are all mid-range, GTX 1660 is in the transition between mid-range and low-end.