This is a silly, self-defeating argument.
Wages aren't determined by "worth". Wages are dictated through negotiations, and they are set based on the worker's negotiating power. If a worker is incapable of negotiating, nor does he have negotiating power over their company's representatives, then he is bound to get the raw end of the deal.
This is precisely where unions and worker's commissions play a central role in the problem. When an isolated worker tries to negotiate with the company, more often than not he faces professional negotiators skilled in cutting down salary expenses. The odds are, from the start, stacked against the worker's interests. This problem is mitigated with the help of an organized worker force, as they can provide professional services negotiating job offers and leverage more power over the company's representatives. Therefore are able to get much better deals than the average worker acting alone.