Those studies do not refer to item volume, they refer to monetary value.

If a business can earn more by selling 5 cars worth half a million each per year, instead of trying to sell 20 or even 30 Cars under 40k to average people their entire business model will shift to cater to billionaires and multi millionaires.

The bulk of average people are becoming irrelevant to the current capitalist market, that’s the point.