There is difference not because other regions play less, but because like you said, Brazillians pay $17,71. But $17,71 equals R$ (Brazilian Reais) 63,45. Which is a huge slice of cake from what people get paid. It ends up making brazilian pay much MORE for the same product.
Which also means that if all prices were equal, less people from other countries would buy anyways, even in THEIR servers. It is not “unfair” to pay differently. If someone wants to pay less, let them move to Brazil and pay “less” as they say, for example.
What IMC did was cutting of potential buyers. They made their profit from “unfair” to zero to all SA, EU and CA players that play on NA, which should be International at the first place. People who played with friends, who made bonds with NA players and even have guilds way before SA server showed up.