GSM Arena reports that a cheaper Apple iPhone is under production "with a lower memory capacity and the new 8GB flash drive is being manufactured by an undisclosed Korean company" targeted at emerging markets. The current iPhone 4 has 512MB of RAM, and it seem possible to cut this to as little as 256MB, since the first generation iPad only has that much memory.
No word on whether the cheaper iPhone 4 will retain the current 640 x 960 pixels, 3.5-inch retina diplay of the iPhone 4 or the lower resolution 320 x 480 pixel 3.5 inch screen of the older iPhones. Since the new iPhone 5 (or 4S or some other similar name) will reportedly have a larger screen it seems to make sense that the cheaper iPhone will have a retina display.
How much? The current iPhone sells off contract at a bit over US$600, depending on your location. A new cheaper model should sell at the US$300-400 range. If Apple wanted to create an even lower end model, they could just continue producing the iPhone 3GS.
Android with 480 x 800 screens are now available for as little as Php17,000, and I expect to see it going into lower end phones by later this year or early next year. The lower resolution 320 x 480 pixel resolution will become the standard for Android phone at the Php10,000 range, with the LG Optimus One already available with that specification at that the price.