but they're often low because they're selling bottom barrel quality goods (like electronics with cheap capacitors that fail quickly or clothes with lower quality fabrics & sewing that don't last). Even products that look the same as other stores will commonly have a Walmart specific SKU that uses cheaper components.

Sadly, this is what customers want. When given the option of a 30$ belt that lasts for life or a 5$ belt that lasts one year, many will go for the latter, and this is who Walmart caters to.

So? People clearly prefer cheap the majority of the time. In the age of the Internet, high quality is a click away.