There is some questions relation dropship business at Quora website. Where do most dropshippers order their products? Why do sellers scrape ASINs? Is there a way to automatically add a product from Amazon and other e-commerce platforms to your store?
A huge number of dropshippers source products from apps specifically created for the purpose of aiding drop shippers. Oberlo, eBay, AliExpress allow dropshipping. The easiest way to dropship from Amazon to Amazon.
Some people find products from inside of the target country like USA.
Many companies scrape Amazon to pull valuable data that is either not available via the Amazon API or if they are unsure how to pull via the API.
Also, from a sellers point of view, this gives us valuable information. There are lots of variations in prices at Amazon and sudden discounts on various Amazon products in different locations. Sellers spot this information and use it to resell products or recommend some.
API usage is easy and cheap. But not all platforms offer the API and API has some limitations on data provided.