Regarding the former, I would be extremely wary of paying a demonstrably "competent engineer" to do work in a platform they were not already immersed in. Total years programming, even on seemingly similar platforms, doesn't translate into ability to deliver a high quality, robust product on the target platform in a timely manner.
To give a specific example, successful iOS development requires a combination of UX design intuition and finesse, similar to what you'd need in web development, along with the memory management and performance tuning skills more typically seen in the embedded and C++ game development world. The reason competent iOS devs are expensive in America is because it's hard to find people with these combined skills, who don't want to just make their own stuff. There are many examples of lackluster apps in the iTunes Store where the developers clearly came up short in one of those areas.