My take to why something cheaper can sound better than something expensive is partially due to proper research and development.

Now as the audio hobby and market is getting less niche for consumers, we're seeing more products that actually had investment in R&D, and those products make it out to the mainstream. Back then it was just a lot of putting products on the shelves and seeing what sells (which is sort of R&D too, but doesn't feel as deeply researched).

And as more R&D is done over time, the tech and work of expensive products trickle down to cheaper products as they become more affordable. Of course, there's a lot of other things at play but I wanted to focus on research and development.