Boost Mobile did this recently when my wife and I switched cell carriers. They advertised a $30/month/line plan (after a 3-month introductory period at an even lower price), but we are now paying closer to $45. This has pissed me off enough that I want to look for another carrier, but this seems to be SOP for this industry. Telcos behave like nothing less than a criminal cartel, so I was hardly surprised by this play…
So it's not actually industry-wide... and hopefully even serves as a differentiator?