This was addressed a long time ago here:
(A number of players on Line in the US this week confirmed a $1 price difference between IOS and android phones. One player checked a number of prices across countries and found the differential continued between the two platforms. This is player-confirmed, not SG, but you can of course see SG’s statement above.)
Additional threads:
Price difference between android and iOS? - #3 by Rook
About VAT taxes affecting European’s VIP purchases:
VIP Pass (1.10) Questions & Discussion - #36 by Maldoror