For Zephyrhills brand they charge exactly the same per gallon for it at the stupormarket as they do for “pure spring water” (although I sincerely doubt it is from a pure spring). For some brands, the cost of the fancy potable water is almost double that of the distilled. That makes no economic sense.
But bottled ‘pure drinking water’ just comes out of the tap, or out of some spring or well, or even a municipal reservoir. Distilled water must be evaporated and condensed back, which requires energy (it takes a lot of heat energy to boil water from liquid to gas). It should cost more. Even if free solar energy is used, the apparatus and precautions to keep it deionized must cost money.
We know the water is indeed distilled, as advertised, because it doesn’t create solid mineral deposits in our appliances, and I use it to clean lenses and mirrors, where even the cleanest spring water would leave spots.
By the way, I used to live in Lutz, near Zephyrhills, the wellfield where they get their water is the same one where St Pete and Tampa get theirs. Its good water, but its just tap water.