Unlimited SMS has been the norm for a little while now (5ish years maybe?), but it wasn't too long ago that the lower tier plans for every mobile carrier in the US (not sure about elsewhere) had a per text charge, possibly after hitting a low monthly limit on free texts, or possibly with no free texts at all.

> every phone plan I've ever had since the first iPhone

Exactly... You realize there was a time before then, right?

In the mid 2000s, texts cost between 10-20c to send, unless you bought a bundled plan, which weren't actually that common then, and even then you were limited to usually 200 texts/mo.

http://www.consumerreports.org/cro/aboutus/mission/viewpoint...