said by TKJunkMail :

And the method of calculating cost by "Mobile Jones" is, as usual, bogus. The cost to the cell provider isn't on how many bytes are transmitted. The cost is based on use of a channel(from a limited number of channels) on the cell tower and how long it takes to grab the wireless spectrum, establish the connection, and then transmit, and then take down the connection. Every time someone sends a 20 byte message, all those costs are incurred and they far exceed the costs of some theoretical bandwidth usage. And then every time a new message is sent(20 secs later for example), the whole process starts all over again.