At some point, Amazon customers are only willing to pay so much. Unless Amazon gets far more productivity per person-hour than its competitors, it can’t afford to pay wildly more than its competitors are paying.
If Amazon service declines, or parts of the business aren’t sustainable, as I mentioned, no great loss. People having jobs that allow them to live with some dignity and control over their work environment is superior to the American consumer getting more consumer goods shoveled into their living room at the lowest price possible.
There will always be non-Amazon jobs, and if Amazon is the only employer in town, that’s a policy failure to be patched.
The risk of taking away their best option in hopes that someone else in another town will get a better option will appeal to some, but far from all, as they cast their organizing ballot.
Unions can, and often do, overplay their hands when negotiating. Adversarial systems, and competitive unions force unions to demand best of industry contracts at every corporation they go to.
To draw a football analogy, every unions wants a Christian Kirk contract, and every contract after that must be a Christian Kirk^2 contract.