Cost of labor is based on supply and demand not the value created. If there were more engineers capable of creating those JS frameworks than there was demand for they'd get paid way less and whoever was paying them would pocket the difference.

While a "Javascript Framework engineer" is a very neutral example how do you feel about the engineers working on ads, making exploitive predatory video games, gambling apps etc. etc. they can get paid even more yet the net value they create for the society is negative.