SMS is a big money cow for the cellular phone industry. Since it is unregulated, they can charge what the market will bear. Interestingly, that is now approaching 20 cents a text. That's 20 cents a text for both the sender and the receiver. Since the text probably costs about 1/20 of a cent to deliver, that is basically all profit. It probably costs more to do the accounting and bill you than the actual message. In the rest of the world, there is caller pays, which basically means that you don't pay to receive texts or phone calls. Not so in the US. Of course, we also have unlimited local calling from landlines which is unheard of in most of the world...
The real interesting thing about the AT&T/iPhone2 deal isn't the offense of the increased prices, it is why the increased price is necessary. Under the old Apple/AT&T deal, Apple sold you a phone at full price, you got a good price on phone service with SMS, voice and unlimited data, and Apple got a kickback on the service from AT&T to the tune of $10-$20/month. The advantage to AT&T was that they didn't have to subsidize the phone and Steve Jobs would market for them with the latest hot, must have product from Apple.
Now, with iPhone2, AT&T doesn't have to give Apple $10-$20/month, although they do have to give Apple a couple hundred up front for each handset (the subsidy). They have gone and added an ADDITIONAL $15/month onto what they were already collecting. So, do the math:
New iPhone $299
AT&T subsidy to Apple - $200 (approx)
New, minimum, monthly increase in revenue for AT&T - $20
Break-even point on subsidy - 10 months, max. (less if you add $5 SMS plan)
If AT&T kept the existing payment plan, they would probably see pressure from their other handset manufacturers to match the Apple price point (probably another significant reason for raising charges for iPhone) to there would be a fair playing field. However, they would hit their breakeven point in no more than 20 months, still better off than before where all that money was flowing to Apple.
The price-supply-demand equation is particularly interesting on this offer because both companies feel like they come out ahead. Clearly, AT&T is applying their regular business model and looking to attract customers who are locked into their service via the iPhone. They take a charge in the short-term, but they are counting on gaining new subscribers (which is harder to do now) and locking in a loyal, higher-paying clientele for years to come. Apple has figured out that the strategy of "devaluing" their iPhone handset by allowing AT&T to subsidize the cost will actually spark a lot more sales and they will blow through their 10 million unit prediction with a lower priced handset without really impacting their business model revenues for current or future earnings (they make up for lost revenue sharing with AT&T in the volume of sales). Consumers, behaving somewhat irrationally, will fund the whole enterprise, buying loads of iPhones at a lower cost of entry, but locking themselves into costs that are actually hundreds of dollars more over the life of their contract.