What motivated me to purchase a gun was a spike in crime in my immediate neighborhood - literally my neighbor across the street (carjacked in the middle of the day by two kids who put a gun in her face as she sat on her porch) and a neighbor about 8 houses down who's home was invaded in the middle of the night while she, mercifully, was out of town.
That type of brazenness shakes me. I have four small children, a wife, and a mother-in-law in this house. If someone comes through that door at 2AM, I've presently got a machete and a hatchet to defend myself and my family with. That's not going to cut it (so to speak).
So there are several things I could do: Get an alarm system, get a dog, get a gun, move, or some combination. Financially, alarms and dogs are recurrently costly. As a practical deterrent in a physical fight, alarms won't do any more immediate help than calling the police would; dogs would though, big ones at least. The shotgun I'm getting is under $200. The security cabinet for it is about $300. That's comparatively inexpensive.
One of the reasons I'm getting a shotgun is precisely because they're big and heavy - not easy for children to pick up, load, and fire, unlike handguns.