Why does it really matter, so long as your development PC is sufficient for the specific game *you* are building?
but it seems there are more fundamental questions to be resolved first. such as does a given title even require an "average PC". not all games are skyrim.
Last I checked, the actual "average PC" has a dual core CPU, 2 GB of RAM, and an Intel Integrated GPU. Steam survey represents a set of people who regularly play games on Steam, which pretty much guarantees a skewed picture of the world (most gamers, by the numbers, play browser and mobile games exclusively).