Back in the WEP/WPS days it was easy enough to use aircrack-ng and get access to a network. Anything public is likely to be slow and probably no access to open ports or manage it in any way.
I'm paying ~$45 CAD/month for a symmetrical 500Mbps line and I think its worth it. I'd never share this with anyone I don't know because my name is on it, anything anyone does will come back to me.