US phone companies are infamous for charging extra for things that should be free, or even cheaper than the default. This started with touch-tone dialing back in the 70s. It's all "creative pricing", designed to get the most possible dollars out customers, given infrastructure costs that are essentially constant. I hate it. The people who actually USE their phones enough to justify flat-rate plans are less unhappy, I think.
OTOH, I pay about $20 for (up to) three months of service on my daughter's pay-as-you-go cheap phone. That includes 60 "minutes" of air time (this is supposed to be an emergency-use phone), and incoming/outgoing text messages apparently count as 0.3 minutes. That's pretty reasonable. (The phone itself was "free".)