To put some numbers to it, if we look at pre-revolution France then nobles constitute <0.5% (120k out of 28 million as of 1780, source https://www.thoughtco.com/french-revolution-pre-revolutionar...) of population, the 'first estate' i.e. clergy another 0.4-0.5%, the bourgeoisie (which would match the professions that we'd consider "middle class" nowadays") would grow from 3% to 7% over 18th century, and 90%+ people would be in the lower class.

In essence, if we want some sweeping generalizations and be generous, then assuming 1%/9%/90% for upper/middle/lower class is roughly in the ballpark for most societies until the 20th century.

So while the noble families are nowhere near 10%, it's not entirely wrong to assert that the top 10% including all the non-noble bourgeoisie, the merchants, doctors, lawyers, officers, etc, would have the means and desire to care about fashion.