Comparing the hardware and software features of the iPad, iPhone 4, and iPod touch is relatively easy. Comparing their costs is another matter, though. It's not just a matter of the price tag - it's also the cost of wireless service over months and years.

These less-obvious costs can make a device that looks like a deal very expensive over the long-term or something that seems pricey now look affordable.

This chart compared the costs of the three devices over two years to give you a fuller picture of what owning them will truly cost.

Comparing Costs: iPad, iPhone 4, and iPod touch

	iPad	iPhone 4	iPod touch
device cost	$499 - $829	$199 - $299	$229 - $399
minimum monthly 3G/MiFi plan	$14.99	$44.98	N/A
maximum monthly 3G/MiFi plan	$50	$94.99	N/A
required contract?	No	Yes	N/A
contract length	N/A	2 years	N/A
minimum total cost of contract	N/A (3G is optional)	$1,439.76	N/A
minimum total cost of device over 2 years	$499	$1,638.76	$229
maximum total cost of device over 2 years	$2029.99	$3,778.76	$399

SOURCE : http://ipod.about.com/od/ipadcomparisons/a/costs-ipad-iphone-touch.htm