Not sure this is reality; or that a meritocracy for webdevs exists.
In recent years, it seems the quality of big "prestige brand" websites (not exactly big tech) is declining, to the point of being unusable on mobile browsers or throttled connections. Not because of technical trade-offs, but reliance on frameworks to achieve "demoable effects" instead of real world features or usability.
We're more than fifteen years into "ajax" and today's kids simply can't do it without burning 10x the cpu cycles and bandwidth. To me it seems there is a decoupling between the utility of webdevs and their pay, and some sort of market failure is occurring.
Machinists own their own tools, in general... and I knew a CNC machinist who quit, went somewhere else, and came back to the shop I was working in over the course of a few months... they aren't easy to replace, even in a job shop. The equipment is a sunk cost, and if you don't have someone who knows how to use it, you're wasting money while it's idle.
Expert machinists using fancy equipment in a factory don’t really have the same ability to just go to a competitor, so they can’t negotiate a raise.