In *our* case, we have solar power system that absorbes most of the heating costs, and our monthly bill to pay off the units is ~$100. I know that we're saving money, but it's difficult for me to figure out the break even point.
So, in some cases, you make the argument that heat pumps are simply more convenient. Whisper quiet. Heat AND cool in the same system. That argument, frankly, is what convinced my wife when we bought a house without central AC.