Auctions was one of a dozen or so large failures on the part of Amazon to find a profit center. eBay wiped the floor with them and Amazon gave up relatively quickly. Since then, eBay has generated over $15 billion in profit in auctions, a figure Amazon struggles to match in its entire retail history despite the scale difference.
All these years later, eBay is generating ~$2.3 billion in operating income and their auction business is under no serious competitive threat (it is a slow growth business however, basically fully saturated). Amazon's huge retail business is only barely able to match the profit of eBay's auction business.
The ultimate value in Amazon of course wasn't retail. For eBay, the value is actually in the ecommerce.
[1] 2001: https://www.zdnet.com/article/amazon-auctions-losing-momentu...