I assume your comment is that Amazon would lose money if a union happened?
I have had situations where it was not allowed to move a computer monitor from one cube to another - that had to be done by a union employee. Literally taking a unused spare monitor from one desk, and putting it on another employees desk where it was need. ...and there was a formal requisition process to get that done which took two weeks to get through approvals, assignment, and finally have it done.
I have had union workers walk off the job during a major system outage because their facility managers forced them to take their break time. The whole company was down - it was all-hands-on-deck outage due to Hurricane Sandy. The actual union workers wanted to help us get the systems back online for the company, but the union rep wouldn't let them work.
I have had great workers quit or refuse jobs with our company because they knew and loathed the union - not the company, but the UNION.
I don't have any problem with unions at companies that protect the SAFETY of workers, as they are needed in various industrial jobs. ...but at a TECH companies where workers are making six figures, have matched 401k plans, and safe and comfortable desk jobs? ...it just screams "ridiculous" to me.
The union is not superfluous to the employees- it is the only thing negotiating on their behalf in a power-imbalanced, often exploitative situation.
The union is not superfluous to the employer- it is actually a hostile counterparty in terms of wages and exploitation.
Thats not to say the added bureaucracy is always welcomed- it sucks.