It's generally true but there are counterexamples. For starters, in most of the world, 15 years ago computer programming was something geeks did while the rest of people were building real careers involving oversight of buying and selling stuff.

Fast forward today, programmers rake serious money getting better than average salaries, in some places several times more than peer salaries. But supply also increased several times. It's just that demand increased faster. I think that if supply would fail to increase we'll see smaller wages today as the market will fail to evolve.