Actually that's simplistic and wrong. for decades it's been more about losing benefits and conditions than money. Cash is the first thing that negotiated away.
Ever since Reagan's union busting activities in the 80s, unions have been waning. What else else has been middle class earnings. People in jobs that used to be union have seen their wages and benefits stagnate for the past 30+ years.
This continues to harm our economy. No matter how many times Republicans talk about trickle down, it will never be true. The reason our economy expands is when those in the middle and lower-middle can afford things.
As unions' power have waned real wages, benefits and mobility have been dramatically harmed. You can wax poetic in hatred of unions all you like, but the reality is their demise has been the demise of the middle class. It has reverberations throughout all sectors of our economy.
By the way, the drivel that unions drive jobs overseas is just that. No one in union-filled MA or non-union NC is going to make Nikes for $4/day like they do in Viet Nam. No one in SC or MI is going to build cars for $30/day like they do in Mexico.
If you want third world wages and benefits, you'll live in a third world country.
With all the power going to employers these day, we are on our way there.