Even the gas vendor in a country with famously low gas prices and an aversion to pricing in carbon seems to put it as a close second, well ahead of propane or oil on operating costs.

You say $1500 saving but that's against resistive heat, not heat pumps, which are only 150 to 350. Which could be small enough a difference that providing cooling with one system may cover it.

And those are only operating costs, and I'd guess if you didn't have a gas grid magically installed for no cost, then propane or oil are the two options you'd more realistically go for rather than pay build a gas connection, whereas a house without an electric grid connection is pretty rare and could be considered a sunk cost in most cases.

Obviously for many existing homes you do magically have gas pipelines for free, but in the context of new builds, you'd want to compare those costs.