>there's welders that can weld garden gates, then there's welders that can work on underwater pipes
Like any other blue collar skill welders are primarily compensated for the skill/experience required to do their job and the amount of inconvenience, discomfort and/or danger that comes from the setting in which their job takes place
Welding fancy alloys for pressure vessels takes more skill and is therefore compensated better. Welding together railings is much easier with much looser quality control so it's not compensated as well because more people can do it.
Doing either of those things in a heated and air conditioned shop is going to pay a complete pittance compared to doing them in the mud in the middle of nowhere, underwater, in a confined space or an otherwise physically demanding and/or dangerous environment.
Like any other blue collar skill welders are primarily compensated for the skill/experience required to do their job and the amount of inconvenience, discomfort and/or danger that comes from the setting in which their job takes place
Welding fancy alloys for pressure vessels takes more skill and is therefore compensated better. Welding together railings is much easier with much looser quality control so it's not compensated as well because more people can do it.
Doing either of those things in a heated and air conditioned shop is going to pay a complete pittance compared to doing them in the mud in the middle of nowhere, underwater, in a confined space or an otherwise physically demanding and/or dangerous environment.