I did some work with Verizon and an IoT customer was asking about SMS pricing and the VZ guys laughed and said it cost less than a penny for every 1M SMS.
and that’s only because an accountant demanded a cost of goods sold!
Continuing that behavior until everybody’s grandma had iMessage, is a large portion of why I don’t trust a telco!
(Not building out the full range of rural etc network they promised to, while cashing all of the government subsidies, struck me wrong as well.)