This is correct. A lot of people don't realize that Amazon actually makes more money from Marketplace (3rd party sellers) than they do with their "Sold by Amazon" products.
The store I work for sells on Amazon and we've listed things that Amazon doesn't sell (and never has sold). Each time we did that and the product sold well for a month or two straight, Amazon would start selling it for less than we were able to (less than the wholesale price we were getting the products for!), forcing us to stop selling it.
If Amazon really makes more when we sell it than when they do, there's no reason they would have undercut us by that much every time.
edit to add: In case it matters, the types of products we this happened with were coursebooks, toys (from foreign manufacturers), and wall and desk calendars.
On any individual product, Amazon makes more when they sell it, most likely. But the point is, that there are way more products sold by 3rd party than within Amazon. So in aggregate, they make more on 3p.
It may be context dependent: today they have many high value uses for capital, better than using it for filling a warehouse, but in the future ,this could be different.
