Let's unpack this a bit.
Isn't the revolutionary aspect of capitalism precisely the act of aiming to undercut your competitors? This capitalist-ethic apologist stuff you speak of makes my head spin. Am I, as the consumer, supposed to spend extra money (sometimes as much as 30-40% more) just because it's ethical to support a business in my own country? Isn't purchasing from a domestic retailer sign enough of my support? What's more, I am invited by the retailer to justify away their higher costs as some second-order act of ethically sound solidarity? We live in a world of globalism. I am buying made in Japan jeans... from Japan. Denimio isn't the only business out there that sells stuff below SE's prices, and I can't imagine that every one of them is "shady".
Don't get me wrong, I patronize SE when I can and y'all's customer service is absolutely tops, but to imply that the consumer should even enjoy spending extra money because such gestures are ethical?
We approach a dangerous ethics when such ethical imparatives themselves become a luxury commodity, available only to those with disposable income. No?