It's somewhat of a weaker argument, considering that in most of the world MTs (mobile-terminated messages) are free, with charges applying only for MOs (mobile-originated).
Also, even in the US, a combo voice+text plan with heavy texting is still going to be cheaper for a combo voice+data plan, so average user ends up paying more money, not less.
Mobile plans vary significantly between countries. Using the US pricing structure as an example simply doesn't work. Just because a data plan is more expensive in the US doesn't necessarily mean it will be more expensive elsewhere.
Also, even in the US, a combo voice+text plan with heavy texting is still going to be cheaper for a combo voice+data plan, so average user ends up paying more money, not less.