Even if deaths are a full measure of cost (and they are not), one should also consider the benefits. Per death, does society benefit more from cars or guns? What are the implications for public health in these two areas?
Although not a statistical statement, there is a noticeable association between when the 1994-2004 assault weapon ban was in place and the observed decline in gun-related deaths. That ban also contained other provisions that will have affected availability of guns.
A decline of more than six thousand deaths per year appears to be associated with that legislation over the ten years before it expired.