Elementals get 2 + Int modifier skill points per hit die, minimum of 1.
Elder Elementals have a 10 Int - no penalty, so 2 points per hit die. Anything smaller than that has an Int penalty, so 2 - X (min 1), or 1 point per hit die.
If Elder Elementals have 2 skill points per hit die, and all other elementals have 1 skill point per hit die, "pretty much double" is about right
(I suspect the Fire Elemental stat blocks are incorrect, since their Int never goes above 6 but the skill bonuses are consistent with the other elementals; I haven't checked the errata.)