I think it’s important to separate high end full service salons from the smaller places with names like “Turbo Nails 2000”, staffed mainly by recent immigrants (usually Vietnamese?). Your lower end places may actually do BETTER in a mild recession, as when people are forced to tighten their belts they more often scale back in level rather than cutting things out entirely.
Also, when people can’t afford big expensive things, they tend to spend more on small luxuries. Think of it as relative vs. absolute cost. This is why I’m unsure on the future of Starbucks. I already can’t understand why people buy their $6 drinks (I sometimes buy a regular coffee and add sugar and creme, which totals around $2). But clearly there are a lot of people who disagree with me.