It is a one-day conference and we fill the day with talks on engaging topics for the audience. (We're techies, so this works better for us) There's been 10-18 attendees and this has been working well as long as the room we have been in has had the right size. It is invitation only, and we're struggling to keep the invitation list from growing too quickly. We're taking turns giving the presentations, so we have a reason to keep inviting the same people back. We order take-out for lunch and after the talks we go out for dinner.
This is dirt cheap. The admission price is really that you have to prepare a talk once in a while. We sometimes charge a little bit to cover costs for coffee and snacks and we have made an investment in a HDMI capture card.
The most striking similarity with the "Tiny Conferences" of the article is that it is definitely the conference I get the best value out of. I heartily recommend organizing something like it! :)
(If you are super curious, recordings mostly in Norwegian are here: https://www.youtube.com/channel/UCiAz5MrT56_p2DCt0D4fz8w A few are in English, and some are captioned in English)