The difference is the power imbalance due to the company keeping information secret. When information asymmetry exists, the party with less information is at the mercy of the other.

Your example of products being purchased is a completely different paradigm due to many reasons. The consumer information is available to the company through many avenues such as market research and affiliates. The company generally conceals the cost of producing an item. The scope and duration of the transactions are also majorly different. Let's also remember that the price for the object is the same for everyone, yet you are offering different pay for the same value to the company. That's the problem.

If we really want to go full capitalist libertarian and let markets decide everything, then let's do away with all the protections. I don't want to live half in one system and half in another. Why should we have protected classes or offer accommodations for disabilities? I think you'll find the answer also supports other workers rights, such as the ones being discussed/proposed here.