Text messaging flows through a pipe... that is, in any given area there is plenty of room for more text messages in flow, and the only way the system fails is if there's enough to fill the pipe. Unused bits of airtime are like empty airline seats, they're worth $0 once the time passes.
So, does 50 cents a message seem reasonable when e-mail is charged at the data rate which is much cheaper... and AIM,Skype, Google's products, MySpace, Facebool, etc. all also travel over the data pipe?
SO, there it is, plain text messaging is going away.... and it's going to be a lot like the old days of Prodigy and AOL where you have to select which protocol to use to reach your friends.