Prices are set by what the market will bear, not the cost of providing the service.
SMS is the most widely used data application in the world with close to 4 billion active users.
It is also one of the most expensive data applications in the world at more than R3500/Megabyte.
Networks worldwide have realised that lowering call costs and subscription costs are much more effective in attracting new clients, than lowering SMS costs. Hence most have systematically lowered call costs, and very few have significantly lowered SMS costs. Those that have significantly lowered on-net SMS costs experienced problems with spam, which resulted in churn.
Provided there is adequate competition, there is pressure on networks to reduce prices. Hence the focus should be on eliminating uncompetitive practices. Agreements not to compete, such as the agreement not to allow cross network A2P SMS traffic, is clearly uncompetitive.