Yes, at least for me it is. My pre-paid plan (~$14/mo) gets me 4GB data but only 50 SMS. I also get 3GB of free WhatsApp data. There is no prepaid plan with unlimited SMS.
Woah. I knew there were still places that charged for or metered SMS use, but I had no idea that the restrictions were that severe.
Funnily enough the volume of scam calls and txt that I receive via WhatsApp is why I have it disabled.
The only reason I ever use it is because we sometimes need cross platform group messaging to organise plans with other families or school groups, then I delete the app again
Quite shocking, yes. SMS used to be free in the early 90s until the providers figured out that they can charge for it. They priced the 140 byte transmission at 0.20 CHF in Switzerland, and in some plans you still pay 0.20 CHF for 140 bytes over SMS, while you can get unlimited data.
EDIT: out of curiosity, which country are you in?