On the contrary, it's economics 101. I have a feeling our disagreement is due to definitions so let me be more specific about my intended meanings.
There is a minimum price at which you are willing to not switch vocations and there is a maximum price at which you can be profitably employed. The latter is what I was calling value, as in "value to the company." Relative bargaining power determines where on that spectrum your salary will be. It's arguable that the final price is "value" but that's not the meaning I intended. What should happen is a question for the philosophers. What does happen is up to us.
The Wapping dispute is an example of a union failing to recognize that the value (same definition I was using above) of their employees had fallen below their asking price. Sure, it happens -- I have no doubt that unions increase friction, which is bad and hurts the economy. But underpaying workers "because you can" is also bad, also introduces friction (increased need for loans, decreased ability of workers to bootstrap), and also hurts the economy. So I don't buy the argument that one is better or worse. As far as I'm concerned it's a zero-sum power struggle, philosophically and morally speaking. I'd rather be on the winning side and I don't begrudge others for wanting to be on the winning side.
I think this is the hard part: what is the value according to which people should be paid? Who should decide it? Not easy.
It gets particularly hairy when technological change has an impact on value. This is happening faster and faster.
Consider the classical example of Wapping dispute [0] where old hot-metal methods of printing, which unions sought to protect, were replaced by electronic publishing tools and printing machines. Today, it would look quite funny if papers still had to employ Linotype professionals to be able to print things in newspapers. The more acute concern is whether publishers print anything at all on paper, or if everything is in the net. If the unions could decide, of course you couldn't publish in the net, because it is destructive to jobs in the printing industry.
At some time, the commercial "value" of Linotype operators was very high. Now it is only historical; as a commercial operation, the machines have gone to obscurity. Who should have decided the value of those workers? I think the only one who really can decide is the one who owns and runs the operation. The unions mostly have an incentive to preserve the status quo - while happily accepting a change in other businesses, if it benefits them. No doubt that the modern-day Linotype operator would see it fit that he uses his union pay to buy an iPhone.
[0] http://en.wikipedia.org/wiki/Wapping_dispute