BusinessWeek reports that AT&T is considering a discounted limited data plan for the iPhone at $20USD per month option. AT&T currently only offers a unlimited data plan for the iPhone for $30USD per month. The data transfer cap for the rumored discounted data plan is yet unknown. Considering it’s $10USD less than unlimited then the cap should be around 256MB or 500MB. If it’s anything less it’ll be a complete rip off at the rumored $20USD price. What do you guys think?

Analyst Richard Doherty claims that this additional data plan option is being driven by Apple, which wants to offer a lower-cost entry point for the iPhone.

The exclusive U.S. iPhone service provider is considering cutting the price of its monthly service package or offering a range of lower-priced plans, say people with knowledge of the company’s thinking. One plan that could be introduced as early as late May would include limited data access at a $10 monthly reduction, the people say.

The possible price cut likely reflects the back-and-forth between AT&T and Apple (AAPL) as they work out whether and under what terms AT&T would remain the sole U.S. iPhone carrier. Apple may want flexibility in pricing as a condition, analysts say. “We understand it’s part of the extension [of its contract] that AT&T wants to maintain,” Richard Doherty, director at consultant Envisioneering Group, says of the prospect of lower data-plan prices. As Apple considers whether to widen its circle of U.S. providers, AT&T may have less ability to balk at Apple’s requests.

The report also hints on the on-going rumor that AT&T is considering dropping the price from the entry-level iPhone to $99USD from the current $199. A prepaid iPhone is also rumored to be under consideration.