There was no r&d done for the ipad, try this, open a program like maya, create a 3d model of the ipod touch (don't worry about rounding the corners as that adds about 5 extra steps to the building)
then now scale everything except the buttons to match the size of the ipad
you will be surprised to see that it looks the same as the real ipad just with out the rounded corners, the borders get bigger, as you increase the width and height, the button stays the same size.
other than the CPU, everything else is pretty much cookie cutter from the ipod touch, they just forgot to hit ctrl + z when the idiots mistakenly deleted the camera before sending it off to get turned into a physical ipad
apple can easily sell the device for $300 and still make a decent profit. Many lesser known companies often sell products with pretty small profit margins because they don't have a name behind them they can only sell based on price and a hope that it doesn't break in like a week
when you sell a item cheaper, you get more people buying the product. would you rather have 10 people buy a product from you at $100 profit, or have 1000 people buy the product from you at $10 profit. the problem is that when blinded by greed, many companies cant see the logic in charging less, they see charging less as less profit with out considering that they will get more customer.
Another benefit from charging less is, you will order more supplies each time, which means larger volume discounts which further lowers production cost which will give you the option to further lower the price of the item and get even more customers.