iTunes offers downloads of Doom & Destiny for iPad and iPhone for 99 cents. (Amazon and Google Play offer it for the same price for Android.) That's tied with our April mention as $2 off list and the lowest price we could find.
Also available is Doom & Destiny Advanced for iPhone and iPad for 99 cents. (Google Play has it for Android for the same.) That's tied with our April mention, $2 off list, and the best price we could find.