[afavour]

That is surely a vast simplification. By sheer operating scale Amazon can ship items at a cost far lower than any brand new “soap company” could. There’s no way you could be competitive on such a low priced item.

[WalterBright]

If you sell 100 soaps for a loss of $1 each, you lose $100. If Amazon competes by selling 10,000 soaps for a loss of $1 each, Amazon loses $10,000.

This is a losing proposition for Amazon.

Spread that over its product line, and it is not sustainable.

[nickpp]

And still countless competitors do exist. They must find some other ways to compete, because your point is valid. It's almost like the human ingenuity knows no bounds...