The iPad may promise a computing revolution, but Apple's new gadget is also a pile of glass, metal and electronic innards - £171 worth, or about half the retail price, according to an independent estimate released Wednesday.

After taking the iPad apart and adding up the estimated costs of the components, the market research firm iSuppli said the low-end version of Apple's new gadget costs about £171 in parts. Manufacturing costs £5.92 more. Combined, that's 52 per cent of the $499 (£328) price for that model.

That doesn't mean Apple's making a nearly 50 per cent profit. There are development costs, marketing and other factors to take into account. Apple didn't immediately return a request for comment.

ISuppli's analysis does offer some sense of what you're paying for.

A lot of the cost, it turns out, is that sleek, user-friendly touch screen. Each iPad contains an estimated $109.50 (£72) worth of components that provide the user interface, or about 44 per cent of the total cost of the parts. For instance, just the glass display, which measures 9.7-inch diagonally, costs $65 (£43).

Second in cost in the low-end, 16-gigabyte version is the memory, which runs about £20. Then comes the battery for £14.

Apple began selling the iPad on Saturday starting at $499 (£328). Versions with more memory run $599 (£394) and $699 (£459), and the company plans to start selling models with cellular wireless capability later this month, starting at $629 (£413). The versions now out offer only Wi-Fi wireless connections.