Many businesses have very small profit margins, so paying staff more or training staff could turn them unprofitable.
When you're buying products cheaply it's likely that somebody (or someone's environment) is paying a price for it. Once you bear that in mind there is such a thing as products being uncomfortably cheap.
(I live in Norway where nothing is cheap but almost everyone earns a good wage. The result is that people don't buy so much stuff but lead good lives.)