A curly-haired little girl with a tiny gold purse, waiting with her mom farther up the line, dashed past us and back again. We would all be standing there a half-hour later when her dad stopped by in a football jersey to take her home for her nap, and her voice would lift into a wail, her arms stretched back toward the crowd of women whose choice of Sunday morning activity suggested a shared commitment to both femininity and thrift.

It’s not easy to commit to both. Femininity is expensive. A tube of MAC lipstick costs $18.50 plus tax and, with nothing pressing on my day’s schedule, it seemed practical to take advantage of a free lipstick deal.

It feels good to get that small win, especially since capitalism so often makes us the losers. Women’s products cost on average 7 percent more than men’s, a disparity known as the “pink tax” because many of the things we’re buying are virtually identical, except that they’re pink. The widest gap I’ve seen was a sparkly pink kids’ Radio Flyer scooter that cost $49.99, when the exact same model in red was $24.99.

This has prompted people like Elizabeth Nolan Brown, a writer and libertarian feminist, to declare that the pink tax is a myth because women could, and should, just choose to buy the cheaper product — that it’s their own fault if they fall for the marketing ploy. Ms. Nolan cites his and hers razors as an example: Pink or blue, razors are just blades set at an angle, so you might as well save yourself a couple of bucks and buy the manly ones. But the argument dries up pretty quickly after that. You can’t save money by switching to a man’s lipstick, for example, because there aren’t any.

Why wear lipstick at all? I don’t usually, but I’ve been trying to wear it more often as I get older and vie for higher-paying jobs. It’s a strategy, and it works. If you look at photos of successful women — whether chief executives or actresses or politicians — they’re all wearing lipstick. These women appear confident, responsible and sure of everything, a surety that starts with their gender. Nothing says “I’m a woman” like a red lip.