[manmal]

I‘m not sure you can blame Moore‘s law here with iPhone CPUs getting 20-30% performance bumps every year.

[hyperpallium]

Since 28nm, successive nodes cost more per transistor, instead of cheapening exponentially as they had formerly. Strictly speaking, this is one of the Moores-related laws, falling under the "etc" of my comment.

tl;dr the performance bumps cost more.