Hello Derrick, the idea of setting wages based on price points of what a firm sells comes from interviews that I have watched recently on business TV shows. The CEOs interviewed described their process of calculating a price point to capture maximum profits and maximum market share, then they described that wages were based on that calculation. Certainly not all firms do it this way, but it was evident that it is a current trend.
Second question... When costs to firms are lowered below a socially optimum level, low efficiency firms, or as some call them "low road" firms, become more prevalent. Let me look for a paper that describes this. I found one that uses low minimum wages to describe how low-road firms are able to compete better with high-road firms. (page 444 in link)
https://research-repository.griffith.edu.au/bitstream/handle/10072/35628/66037_1.pdf;sequence=1
The idea is basically the same, if a cost can be lowered below a socially optimum level by a "governmental" policy like minimum wages, interest rates, environmental regulation and worker rights to collective bargaining, then low-road firms become more prevalent and can drag on wage increases in the labor market.
In my opinion, this is what is happening in the economy now. There is a combination of 1.) lowered costs to firms allowing low-efficiency firms to survive and 2.) increased market concentration creating more monopsony leading to stifled wage increases. Low interest rates is an important cost which to me is below a socially optimum level because low-efficiency operations are surviving more than they should be.
The result is lower labor share which is creating an economy below a socially optimum level.
For me, secular stagnation is just a confusing term to say that the economy is running below a socially optimum level where costs are being set below socially optimum levels by "governmental" policies, which allows low-efficiency firms to survive more.