I have a free 1 MiB/day plan. I only pay €8/year to top up the prepaid SIM. This would be AMAZING in 2005 but now the number of webpages that work on my 2G feature phone via Opera Mini is shrinking. Not to mention, there is no privacy because of the transcoding server. A stock-firmware 4G smartphone would eat through this data in a minute just with background apps calling home.

With the right software (rooted Android, custom clients, transcoding server at home) one could theoretically get all day of use of text- and sparsely image-based services such as email, RSS, SSH, timetables, Lemmy... I'd need at least a data blocker for backhround apps, a kiB meter in the notification bar and a confirmation pop-up for every transaction above 10 kiB (this can be estimated by content length).

This is not really a common or easy attack, especially for any meaningful service (that is probably in preloaded HSTS lists).

It's not like this is the only shared network. In airports millions of people everyday connect to the same network.

The more competitive networks tend to include EU roaming as standard. The ones that charge a lot - like the £2/day mentioned - tend to be the ones with captive customers like Sky, for example, where most of their customers also have TV and broadband from them so they're stuck.