This is simply not true. You (and perhaps most people) may have a difficult time discerning between high and low quality products, but both are readily available. That difficulty may be part of the problem why lower quality products dominate. Though I think it has more to do with cheaper prices. And while it's certainly true that many higher priced items are of similar quality as lower priced ones, higher quality products do exist.

As an example, I'll use flash memory devices (USB thumb drives). I used to consult for a firm that assembled these things as part of their business for use by corporate customers. They would buy flash memory chips from various chip vendors. You can, if you wish, purchase flash memory chips that have passed stringent tests. Or chips that have been rejected by other OEM's. Guess which ones cost more? Some of my client's customers demanded the absolute cheapest possible chips. So my client provided them (with warnings). The failure rates for the cheapest of the cheap could reach as high as 20% in a batch in our testing. The clients didn't care. Sadly, ALL the clients that didn't care were American companies. Not even mainland Chinese companies would use them.

There's a few interesting channels on youtube that deconstruct various products (from shoes to toasters) to see how high quality they are. It's quite instructive at how much different price points can differ (sometimes from the same company).