They're taking on financial risk but I wouldn't call it entrepreneurial risk. They can list any number of products at time, risking nothing but money. There's nothing innovative or novel being added to the world.

The closest thing to entrepreneurial risk is the "creating demand" claim but that seems unlikely to be very true in most cases. In most cases, they're likely capturing demand on Amazon itself by being among the first to list a product.

It seems pretty clear that they're arbitraging and Amazon is taking advantage of its position to out-arbitrage them. In many cases, it seems reasonable to assume Amazon would've tried selling the product themselves regardless.

These arbitragers probably just have to accept that the reward for finding new products to arbitrage is very time-limited, because if Amazon doesn't start competing with them, someone else will.

This is a great example of a ruthlessness, but highly functional, capitalist market. It seems to work out great for consumers, all things considered.