“Teachers will come up to me and say, ‘Make sure you get my good side, make sure you Photoshop this out,’” said Louisa Wells, 26, a photographer in New York City who does work for a local school.

Ms. Wells, who works with lifestyle brands and on the occasional wedding, said she often receives editing requests. “They’ll ask me to Photoshop something that I can’t do without it being absurd,” she said. “A lot of it is adding in hair, or completely changing the shape of someone’s chin. If I do that, you will not look like yourself.”

Emelina Spinelli, 31, who works in digital marketing (with a specialty in Instagram) and lives in Los Angeles, has observed an uptick in questions about how to look best on camera. “My clients will ask me, ‘How do I find my angles?’” Ms. Spinelli said. “They know that to take good photos you have to position your body in a way that looks more pleasant.”

Since its birth in 2010, Instagram has grown its monthly active user count to more than one billion. Multiply that by the average number of selfies and portraits each user posts every day, and multiply that by how many unposted photos they took before picking one for their followers, and you find multiple opportunities for refinement.

That’s just Instagram. People are posting photos and videos of themselves on Facebook, Twitter, Snapchat, TikTok, their WhatsApp profiles, their websites, blogs, on Flickr and more. Narcissus’s stock has never before been so high.

And self-perfection has become big business.

As more people have joined social-media networks, the marketing and selling power of popular profiles has become more apparent, to the extent that the Federal Trade Commission offers extensive guidelines for “influencers” who endorse products. These days, a savvy social-media strategy can convince people to shell out thousands of dollars each for a festival that never happens and can be the force behind a 21-year-old’s $900 million fortune.