Unlimited costs more, I don't pay it because I never use more than a couple texts a month on my personal phone. I'd rather pay 20 cents for a few messages, even though it's extortion, than $5 a month (25 messages worth) and only use $1.20. I can call anyone I know with a Verizon phone (everyone I care to talk to has them anyway) for free any time!
The carriers are taking advantage of the fact that kids and most adults don't seem to realize the value of money "oh, it's only 20 cents, that's nothing". Stupid consumers lead to higher prices, it's a simple fact.
Considering the extreme cost of wireless service to begin with, texting and internet should be included anyway; without the additional cost. But then the companies couldn't line their pockets enough to own 4 houses each!
Same thing with the music services, $15 a month is a lot for those services. It's a convenience vs cost issue and most people are too stupid to realize how much money they loose on conveniences.
I don't understand how sending a few dozen characters over a cell network can justify charging 20 cents. The cell companies should just be happy that you aren't actually calling the person as one second of voice communication is way more data than any text message.
Oh, and @Niva, I hope you're joking (otherwise you're an idiot).
@Niva: Yes, inflation is a problem but 20 cents today would be worth about 18 cents in 2006, not "less than 10 cents two years ago".
And I have to agree with gm0n3y, in that I don't understand why a text message costs so much, as from a data standpoint they are smaller and don't have to be sent in "real time."
About the only reasons I could think of would be start up costs or significant market forces. The former fails because text messages have been around for years and pretty much every carrier supports it. The latter fails because, as I already said, pretty much every carrier supports it and has for years.
Collusion, or greedy apathy seem to be the most obvious reasons for the cost. However, we are not experts nor very knowledgeable of the details so we may be missing some piece of the puzzle.