Em Hermann-Johnson had been following Anne Helen Petersen’s writing for years when, in 2020, Ms. Petersen quit her job at BuzzFeed News to write her newsletter, Culture Study, full time.

“I didn’t hesitate to support her,” Ms. Hermann-Johnson, a 52-year-old substitute teacher in Minneapolis, said. She paid $5 a month for a Culture Study subscription. It would be the first of many.

“I don’t even know how many I pay for right now,” she said. “Five, maybe? Six?”

When she sat down to determine the actual number, it turned out to be 11. She pays between $5 and $10 a month for some and between $38 and $60 annually for others, totaling about $600 a year, she said.

In the last few years, more people are spending a significant amount of money on email newsletters from their favorite writers. As a result, some have also fallen into a familiar budgeting trap: It can be difficult to keep track of how many newsletters they’ve signed up for and how much they’re paying for them.

Despite the surprise, Ms. Hermann-Johnson didn’t consider culling her list. As she read through her paid newsletters — among them from Nora McInerny, a grief writer; Laura McKowen, a sobriety writer; and Catherine Newman, a memoirist and novelist — there were no surprises. All were writers she read, loved and felt good about giving money to.

“I just want to support them and their work, and that’s how I feel like I can do it,” she said.

A Relatively New Spending Category

Hamish McKenzie, one of Substack’s founders, wrote in a Substack post last year that Ben Thompson, a tech analyst who writes the blog Stratechery, had inspired an early version of his company. Mr. Thompson added a paid membership option to his blog in 2014, and within six months, 1,000 subscribers were paying him at least $100 a year for premium content. (Mr. Thompson refers to his own publication as a “subscription-based blog, newsletter and podcast.”)