I don't have a network (it is just me), so that probably makes a huge difference on the cost.  When I had the light version, I had to pay for state returns not in the state I chose, as well as for Corporate returns (since I had fewer of them than I did the other types of returns).  It was those costs that made the full version less expensive for me.  I also don't recall if I also had to pay for 706, 709 and 5500 forms as well under the light version.