The author recognizes that laundromats exist, but doesn't believe that washing machines are a luxury good (his yacht example of 60% owned by the top 1% likely applies somewhere around 60% to the top 30%). This indicates the author generalizes that high density living with shared appliances don't exist or apply to a large part of the population (that density doesn't shift statistics).
A few thoughts, instead of taking 340m people, you need to account for 2% homelessness, another 8% as housing insecure, 30%+ as high density possibly sharing at the apartment/condo building or laundromat level. A small upper 1% that outsource to services.
The infamous Mitt Romney, 47% of Americans don't pay income tax quote can be really shocking when you start thinking about the average American, and the wages that they earn compared to a higher income segment you might be in.