Honestly, I don't think there is any relation between developer salary and computational power. I was just reaching for a possible explanation for this[1] that fits with the theory that people are paid based on their productivity. It is my belief that people are paid based off the supply and demand for their labor. Productivity only serves as a ceiling for compensation and even then, that is only in the long term. Plenty of people are paid more than their production either over the short term or when productivity is difficult to measure. An employer's natural inclination is to pay people as far below their level of production as possible while still filling the job.
It is my belief that the reason that low skill wages have stagnated is not because their efficiency has stagnated. It is because their supply is outpacing their demand. The supply of software developers is not keeping up with demand so their wages are increasing. Neither has anything to do with productivity in my opinion.
[1] - https://lh6.googleusercontent.com/5n4R_Osks_fVsVmedxJKsp9zPu...