Right now if I wanted to compete with Amazon, I could buy 2 or 3 petabytes of storage space and some bandwidth. But nobody would trust me not to lose their data. This is the differentiation that makes cloud storage less of a commodity than it could be. The goal with filecoin is to make it so you don't have to trust me, just some general guarantees about the filecoin network. If amazon for some reason was selling storage on this network, I could compete with them on equal footing (and whoever sold it more cheaply would win).
Many commodities are in close-to-perfect competition. For instance, I don't care if grain comes from England or France, just that it's cheap. While it is very hard to make an economic profit selling grain, many people do farm grain and make enough money to support themselves (The money you pay your workers to survive is one of the costs of producing grain. That's true even if the only worker is you)
If you could make a profit by running a filecoin node on a VPS, everyone would do that. By competing with each other you'd all bring the price down and down until it was no longer more profitable than selling any other commodity (and maybe even lower). So you're right to not expect to be able to do that.
