I sold a book on Amazon and Amazon discounted it. I only made one sale as it was newly added to Amazon, something like 1-3 months after I put it sale, so the logical conclusion is that it was done randomly rather than by some algorithm, as there was no data to conclude that a book with one sale should have a discount. It's as if Amazon deducts millions off its profits and randomly shifts it round to different books, in order to determine which random shifting results in more sales. If Amazon does do this, then it's more clever than we give it credit for. Amazon has billions of products. Google can use PageRank and social media shares to determine site and page quality as links and shares are votes and signals, but the only signal Amazon has are sales, wish list adds, and reviews, which are really shitty signals which mine only had one sale. It's totally random, nothing much algorithm behind it.

If your product is popular and Amazon knows this - they have people who check sales and internet hype -humans will manually discount it for you in order to increase sales.