I guess it's down to Apple obsession with thin design, they need high density ram for that, and supply for high density ram is limited, at least according to a simple Google search, and based on Apple sales number, they must be requesting a lot in comparison to phone makers other than Samsung.
In relation to pricing, aside from requiring specific components, designing a thin device also requires a lot of effort because they have to pay attention to heat dissipation and all that, based on what ASUS said:
http://www.cnet.com/news/asus-explains-why-smartphones-are-more-expensive-than-the-249-fonepad/
Add to that with Apple enforcing their high profit margin... resulting in a very expensive device.