1) The original iPhone cost $499 and had just 4GB of storage. The 8 GB model cost $599.
2) On September 5, 2007 Apple dropped the 8GB model price to $399 and discontinued the 4 GB model.
3) A 16 GB model costing $499 was released on February 5, 2008.
4) The development cost of the original iPhone is estimated to be around $150 million.
5) The display of the original iPhone had 153600 pixels, at a display resolution of 320x480 pixels at 163 pixels-per-inch.
6) The iPhone 4S has 614400 pixels, or four times the original. It has a display resolution of 640X960 at 326 pixels-per-inch.
7) The original iPhone, which debuted only on one carrier in the US, sold 270,000 units in its first two days.
8) The first iPhone took 74 days to reach one million sales.
9) The iPhone 3G, the second version of the iPhone, clocked a million sales in the opening weekend. The iPhone 3GS clocked similar opening weekend sales.
10) The iPhone 4 clocked over 600,000 pre-orders in just a single day.
9) 1.7 million units of the iPhone 4 were sold during the weekend that sales opened.
11) iPhone 4S was the first iPhone to break the million pre-orders mark, clocking the figure the day pre-orders opened.
12) The original iPhone was 11.6mm thick and weighed 135 grams.
13) iPhone 4S weighs 140 grams and is 9.3mm thick.
14) The iPhone 3G is the lightest iPhone till date at 133 grams.
15) iPhone 4 and iPhone 4S are the slimmest at an identical 9.3mm thickness.
16) The original iPhone launched with a grand total of 0 third-party apps. Apple didn't let developers write app for its phone until the iPhone 3G.
17) Apple had sold over 218 million iPhones (all generations combined) as of 31st March 2012.
18) There are over 650,000 iOS apps as June 2012.*
19) There have been over 30 billion apps download from Apple's App Store as of June 2012.*
20) Apple has paid over $5 billion to developers as their share of the App Store revenue.*
* The number includes iPad-only iOS apps as well, since Apple doesn't share the breakdown