While the iPhone price cut follows the general pattern of falling prices, quickly knocking a third off the price of a high-profile product is unusual for any consumer electronics company, let alone Apple.

The price of consumer electronics is always going down thanks to intense competition and the steady decrease of the cost of electronic parts. The pricing is largely determined by Moore’s Law, the observation made by Intel’s co-founder Gordon Moore that the number of transistors on a silicon chip doubles roughly every 18 months. Because this rate of change is described by an exponential curve, it dictates not only that prices fall, but also that they fall at an increasing rate.

Image An early adopter left an Apple store in Manhattan in late June with one of the first iPhones. He might wish he had waited. Credit... Jeff Zelevansky/Reuters

For example, the average price of a 42-inch high-definition television has declined to $1,522 from $1,844 so far this year, an 18 percent drop, according to the research firm iSuppli. Analysts said they expected a 25 percent drop for the year, but it has been more in years past.

Mobile phones tend to be more prone to price declines because the pace of product introductions is faster than for televisions or DVD players. Motorola, for instance, introduced the ultrathin Razr phone for $499 with a two-year service contract in early 2005. Six months later, Motorola realized it had a hit on its hands and dropped the price to $199 in an effort to aim at more mainstream buyers. By the end of 2005, the price was $99.

Ken Dulaney, a vice president at Gartner Research, said that in general starting high and dropping the price slowly was a smart strategy. By starting the price high, manufacturers can gauge early demand and reap greater profit from early adopters who are willing to pay any amount to be the first with a particular device. “It’s probably a formula taught in business school,” Mr. Dulaney said.

That must have been what Apple was counting on. But the size and speed of the price cut alienated some of Apple’s most loyal supporters.