He wrote: "One of our sources claims that Apple’s iPhone prices remain too high for most mainland Chinese customers—the iPhone 5 hardware alone starts at $849 there, versus the iPhone 4 at $500, in a country where the average annual salary is around $3,000 per person).
"The source has said that mainland Chinese iPhone 5 sales are already tapering off as a result of the pricing, which is higher than in Hong Kong. A budget iPhone model would help sales in populous but underdeveloped countries to grow."
Horwitz also says that Apple will release an upgraded iPhone 5S, with an improved rear camera, perhaps in July. He says his sources claim a fifth generation iPad and a new iPad mini - with 'retina' display - will be released in October.
The company announced a record 47.8 million iPhones sold but Wall Street expected more. A cheaper version of the device is seen as essential by some analysts, particularly if Apple is to make inroads into the growing Chinese market.
In response to the results, Trip Chowdhry, an analyst with Global Equities Research, said: "Apple will need to innovate. For Apple to renew growth they need to come up with new devices."
It appears that Apple is already thinking along the same lines. The earnings report reveals a 32 per cent increase in Apple's research and development budget in the final quarter of last year. Apple increased its spending on R&D to $1 billion, an increase of $252 million, compared with the same quarter in the previous year.
Apple's filing says: "The Company continues to believe that focused investments in R&D are critical to its future growth and competitive position in the marketplace and are directly related to timely development of new and enhanced products that are central to the Company’s core business strategy.
"As such, the Company expects to make further investments in R&D to remain competitive."
Yesterday, Apple released iOS 6.1, the latest version of its mobile operating system. Announcing the release, Phil Schiller, Apple's marketing chief, said that 300 million Apple devices are now using iOS 6, which was released in September last year.