Apple acquired PA Semi, which wasn't just an ASIC group, but arguably the best group of processor designers for high-performance, low-power computing. The group previously built StrongArm (a famously high MIPS-per-watt processor in the 90s). It's a much more specialized skillset than normal ASIC dev.

The reason it should work out better for Apple than it did for Sun is

(1) Apple sticks with ARM architecture so they don't have to custom-build the whole toolchain (eg compilers)

(2) Apple ships in insanely high volume so the cost of chip development is pretty low amortized over their volume

(3) Performance-per-watt is really important in mobile, and they're doing it with an amazingly accomplished team in that area.