https://en.wikipedia.org/wiki/Right-to-work_law
Here we tend to call it right-to-work-for-less. The gist of it is that employees aren't compelled to pay union dues if their workplace pays union-negotiated wages. If you think of union protections as something like a private form of OSHA, or say private car insurance, then opting out of paying for them while still receiving benefits is self-evidently not sustainable. Not enough people pay (essentially the same as having too many scabs) so unions can't maintain their bargaining power. The end result is that there are almost no unions in Idaho.
My experience with this was when I was moving furniture as a non-technical day job in the early 2000s. It was $10/hr for warehouse work and $12+/hr working for private truck drivers (you could negotiate your own rate). But if you went across the border to Oregon (a non-right-to-work state), it was at least $15/hr. I had several drivers from California pay me $20/hr for the same reason.
Our warehouse charged $34/hr. In a business where the work is done primarily by laborers, it's hard to understand how it's fair to pay them less than 1/3 of gross income. That's because it's not. Many businesses here charge $75-100/hr or more and pay their employees the going rate of $15/hr. The end result is that Idaho now has some of the highest wealth inequality in the nation:
http://www.idahostatesman.com/news/business/article209332734...
I mention all of this because I get the feeling that non-right-to-work states are enjoying the benefits of unionization without realizing it. It's one thing to argue the nuances of liberty and another to make 1.5 to 2 times as much money (or more) and provide for yourself and your family.
Unionization isn't about raising prices. It's about paying better wages so everyone is better off rather than one millionaire at the top. I think of it as "the person doing the lion's share of the work should receive the lion's share of the income". I feel it's important to really stress this on a site like Hacker News whose readership prides itself on being informed and rising above propaganda.