Economist like to talk about negative externalities; actions by individuals or organizations that create costs for those that are not directly involved. Air pollution is usually the best example; the smog created by a coal plant creates a health cost in the community surrounding it that the owners of the plant do not pay.
Crime is also the source of negative externalities. A robbery or assault have negative effects beyond the the people directly involved: it affects property values, increase policing costs, and has a real effect in everyone else´s taxes. Gun violence is a big part of those costs, obviously, although they are sometimes hard to quantify.
What we can say for sure, however, is that they are not at all trivial: David Hemenway, on a recent book on the subject, points out that gun shot wounds in the leading uninsured expense for hospitals in the US. Most uninsured expenses end up paid by the states, so gun wounds end up costing money to taxpayers.
High crime rates have real social costs - costs that go beyond the cities where most of those crimes are committed. Putting an end to gun violence, consequently, it is not just a matter of safety; it is also a way to save money. As Hemenway points out, it is not just a matter of 2nd amendment rights; the same way regulations and public policy have dramatically reduced traffic fatalities without infringing on the right to operate motor vehicles, gun regulation should be tackled as a matter of public health, not just prohibition or clumsy weapon bans.
What should be clear by now is that gun ownership has a social cost that goes well beyond the cost of buying a weapon. It is the time to take them into account and work to reduce the price for all us.