But they're a demographic that bought them so that they could spend $20+ regularly on video games so you could expect penetration or prices to be higher.
and there are more people in Europe than the USA - but that doesn't mean you ignore the US market.
Even if all things were equal, Nintendo portable is still a huge market. While the lines are blurring, I still think DS is a game device, and iOS isn't - specifically with respect to how much people pay/expect from games. The development costs for DS would be higher - as you'd have to build a longer game, but the so too would the margins.