If claims by Phone House, a Spanish mobile phone retailer are to be believed, it would appear that Google is subsidizing the new Nexus 4 on the Google Play store. Phone House has claimed that LG are selling the devices for a much higher price than that being offered by Google on the Google Play store.
This leaves us two options. Either Google is subsidizing the devices, a not unheard of option, or LG is trying to get a lot more money out of the device by selling to carriers. On the Google Play store, the Nexus 4 is available for $300 dollars, a cheap option to get a contract-free device that can be used with many different carriers.
However, Phone House is saying that LG has offered up the device with a MSRP of $770. LG could by trying to make a massive profit, or Google could be subsidizing. I'm going to guess that it's the latter. Google has a habit of doing things like this in the past, and I see no reason why they would stop now.