Pulling on this:
Substack charges 10%, handles everything and may bring a network - but that means they have control, not you
Memberful plugs into your existing site & charges 5%
Ghost is a flat $80/month but you WILL need a developer
And, Stripe adds ~3% to all of the above. https://twitter.com/Jason/status/1309916875707482112

In part this is a re-run of the question "should I use Medium, Squarespace/Wix/Webflow, or code my own CMS stack?". So, how much control do you want, do you need them to give you an audience, and are you happy writing code to change a font colour?

(Side note: I have huge admiration for everything Wordpress has achieved, but at this point I can't see how they fit into this. I do not want to do patch management on something connected to credit cards)

But amongst other things, in comparing the price of Substack to the price of Ghost, you need to add in the cost of hiring a developer to make it all work.

Hence, when I added a paid tier to my newsletter, I decided to add Memberful + Stripe to my existing Squarespace site (and carried on using mailchimp for email). I worked out that Ghost needs me to install a command-line tool on my Mac to change a font size and closed the tab

(Second side note: notice how we have a whole bunch of great use cases for blockchain this year, from Covid tracking to paid newsletters, and yet no-one bothers with it? A little the way lockdown wasn't a VR moment at all...)

A paid newsletter means giving up reach. Instead of tens or hundreds of thousands of people reading what you said (and that has tangible value beyond ego), you get hundreds or thousands. So can you write both a free thing and a paid thing, or are you happy making the switch?

In my case: my website gets 150-250k PVs each month and my free newsletter has 150k subscribers. Putting *all* of that beyond a paywall would be be lucrative, but would cut off a lot of other avenues as well.