Nexus 7 is less but it isn't too far off from iPhone 5. Remember Google is giving away $25 in Google Playstore credit and $10 in Google Wallet credit. That's $35 extra. I bet 8 gb Nexus 7 is somewhere between $150-175.
iPhone 5 has no special hardware. What makes you think iPhone 5 has expensive build?
This pricing difference shows how harmful subsidies are. If not for the carrier subsidies, retail phone prices would be similar to tablets.
The Wallet credit has nothing to do with the cost of making the Nexus 7. Its a promotion to promote Google Wallet on lots of devices. And it doesn't cost Google $10 per device to offer it.
The Play credit also has nothing to do with the cost to make a Nexus 7. Its a limited time offer that is offset by some profit margin and also doesn't cost Google $25 per device to offer it.
The Nexus 7 has a couple of bits that cost a little more than the components in a $130 Android tablet. And its missing some bits that a $130 tablet does have.
Its also shoddily designed and built, at least compared to a top of the line cell phone. There is more engineering and manufacturing cost in a small device than there is in a medium sized device, for example.