It is mostly PR.

Among all Amazon workers, the median pay is $28,446 a year ($13.68 an hour), a figure the company revealed this year for the first time because of a new regulatory requirement. That’s a worldwide figure that includes full and part-time workers. Glassdoor, an employment site, says average pay at U.S. fulfillment centers has been $13 an hour, according to nearly 900 people who submitted their data to the site.

Amazon’s pay is significantly above the $10.28 an hour that the typical retail worker makes, but it’s less than the $15.53 that a median warehouse employee is paid, according to Labor Department data.

https://www.washingtonpost.com/business/economy/amazons-15-m...

Article is from 2018, but is about a wage increase to $15/hr.