The financial costs is to keep unemployment insurance premiums lower. The more unemployment benefits your ex employees receive, the higher the unemployment insurance premiums. Ex employees are not eligible for unemployment benefits if they are terminated for cause.

Ideally, a PIP in a white collar setting is also for the benefit of the employer about to be terminated to serve as advance notice that they should start looking for other employment. It benefits the employer because if they can start planning and looking for work elsewhere earlier.

Ideally, they do and resign from their position, and the employer benefits here also since there is reduced risk of litigation from a resigned employee, and the ex employee is ineligible for unemployment benefits due to resigning, so the employer saves money on unemployment insurance premiums.

There is nothing special about Amazon in this regard - including the fact that the vast majority of PIPs result in termination.

Heh, I like this one