Advertisers are paying to sponsor the newsletter, to reach the readers. The readers are not paying anything (it appears). The author went with a sponsorship model.

Sponsors are paying $250 to get their message in front of 7,000+ subscribers who are interested in wfh desk content.

The individual readers subscribe for free.

Perhaps that's the price for placing an ad, and the news letter goes out w/ 2 ads, weekly?