"Texting apps are especially costing wireless carriers, which for years relied on the services for the bulk of their revenue.The Messaging Apps Taking on Facebook, Apple - WSJ.com
By some estimates a single text, which may cost as much as 20 cents to send or receive, costs the carriers themselves just one-hundredth of a cent. The rise of texting apps has taken away $23 billion in revenue from carriers as of the end of 2012, according to market research firm Ovum."
Thursday, March 28, 2013
The Messaging Apps Taking on Facebook, Apple - WSJ.com
From a mobile messaging market map