That's not entirely surprising. Unions aren't optimizing for company productivity, but for the conditions and pay of the workers. And conversely, a company can abuse its employees to a large degree while reaping productivity gains from it.
> However Amazon is barely profitable as it currently stands. Since there's essentially no room for lower profitability.
Amazon is "barely profitable" because of clever accounting. They rake in tons of money, and reinvest it into growth. There is plenty of buffer to eat the unionization costs. But of course Amazon may opt to pass these costs to customers instead.
Amazon’s warehouses for example have some serious safety issues which they largely ignore. One example being heavy items being stored in such a way vastly increase the risk of back injury. Stuff can be good for efficiency and a really terrible deal for workers.
It's not large scale or even necessarily generalisable. I don't think a study limited to 83 "Sawmills in the Western U.S." can be presented as an example of unionisation in general.
> However Amazon is barely profitable as it currently stands
Amazon actively avoids profitability... Modern economies do not reward profitability, they increasingly reward the promise of potential future profitability. Amazon is perfectly capable of earning a healthy profit, but it is actively incentivised not to in favour of chasing further growth. Uber, WeWork, and Doordash all exemplify this attitude; although it could be argued that they are incapable of profitability at all.
Companies are actively choosing to remain in the red in order to stack the house of cards that little bit higher, steal a little bit more of their market before they turn around and exploit the fragile and artificially inflated position they've bought their way into.
> The most defensible thing you can say about this is that the cost is primarily borne by the shareholders rather than the consumers.
Surely the most defensible thing is that the workers are fairly compensated and work in humane conditions? We seem unable to convince Western corporations to not use child or slave labour, but at least we don't attempt to justify it by saying "Iphones would be more expensive without Uighur work camps".
The most defensible thing you can say about this is that the cost is primarily borne by the shareholders rather than the consumers. Thus you tend to see that the best unions for workers tend to be in large, established, highly profitable firms with little to no competition. A prime example are the American automakers before the 1980s when foreign competition kicked in. Working on the GM assembly line in 1970 was a very good job.
However Amazon is barely profitable as it currently stands. Since there's essentially no room for lower profitability. The only give is either higher consumer prices or deadweight loss, i.e. fewer customer and therefore fewer (but higher-paid) employees. That might not necessarily be a bad thing, especially to the extent that the average Amazon customer is wealthier than the average Amazon warehouse worker. But given Amazon's extremely thin profit margins, I don't really see anyway that consumers won't end up paying for the sizable bulk of the unionization costs.
[1] https://journals.sagepub.com/doi/abs/10.1177/001979399204600...