Amazon defines this as:
Includes product sales and digital media content where we record revenue gross. We leverage our retail infrastructure to offer a wide selection of consumable and durable goods that includes electronics and general merchandise as well as media products available in both a physical and digital format, such as books, music, video, games, and software. These product sales include digital products sold on a transactional basis; digital product subscriptions that provide unlimited viewing or usage rights are included in Retail subscription services.
2014: $68.513 billion, 2015: $76.863 billion, 2016: $91.431 billion.
Last reported quarter 2017 Q3 it was $26.39 billion, up by 22% from $21.59 billion the same quarter a year before.
Since 2015 it increased by 19%, from $76.62 billion to $91.43 billion in 2016.
Source: Amazon Quarterly Results.