One way is likely through product placement and sponsorship. Just have to make sure not to lay it on too thick or you'll lose readers.

People read newsletters to be informed on certain topics, entertained, or for their curiosity.

Those who find enough value out of a newsletter that does one of those things for them, will be willing to pay for it.

You could say the same thing about books, newspapers, magazines, etc.

I do say the same for magazines and newspapers. Most books however are in a distant category. Their primary purpose is not to extract a dollar from you.

I think if you looked at the newsletters that people are paying for, you’d see they are very different from most of the newsletters we’re familiar with.

The newsletters that are treated like lead generation tools are not the ones making subscription revenues.

You could say that about any online content. And transactable value is not the only type of value to be found in the world.

Transactable value or unique information on some niche topic you're really interested in. Years ago, I subscribed to a (print) newsletter on folding kayaks for example. Of course, that's harder today given the amount of freely available information on the web.

People who are not struggling or cheap? I pay for a couple of newsletters (on Substack).