There are people whose labor is worth $20/hr+ who are desperate enough to accept 8.

"How much value do you bring in?" only puts a ceiling on pay negotiations. Desperation is what drives the actual number.

There are many, many more people like that which is why minimum wage rises almost always come straight out of profit margins:

http://www.nelp.org/content/uploads/2015/03/NELP-Big-Busines...

There is, of course, the matter of the vast amount of economic propaganda saying the opposite. That's driven by what economists call "incentives".