First, that means there is an open, two-sided market and, second, citation needed that that is really the case. Btw., employers can and do also pay based on non-meritocratic KPIs (but depends on your definition of that term).
I'm not a scientist nor am I trying to get into an actual debate on hackernews. I'm just spouting my opinion and feelings on the matter like conversations were done preinternet when someone could just go digging around to find a study to support their argument. Of course employers reward people for loyalty but as someone who has worked in a union environment before, I've felt stifled. I come from a family of tradesmen and unions do wonders to protect the health and future of employees but they are just as corruptible as corporations. They're just corrupt for the people they protect which happens to benefit the union workers most of the time.