I hear a lot of people thinking along these terms, but I think trying to anticipate what you should be making without researching the market can end up in a bit of a disaster.
To know what you could be making from a product you need to put a basic equation into place. Price you source at, against price the product is selling for in your marketplace!
That's the most basic equation you should start with, from there you can then start sharpening that up by factoring in other forces to that equation. For example, competitors, market strength, suppler reliability and so on.
What it all boils down to is that the market itself will dictate what you can expect to make on a product.