David Isenberg emailed me and PLEADED that the Madison folks make this a free WiFi service as he rarely pays for it any more (other than hotels). That is largely my experience. There’s often a free hotspot available in the big cities (I parked recently in San Francisco prior to a meeting and fired up my laptop, only to find several free WiFi hotspots).
I think any local WiFi network based on subscriptions will be a challenge.