>That's nonsense unless your the kind of person who says a cup of instant is indistinguishable from a freshly ground brew
No, it isn't nonsense. And yes, I can tell the difference between a cup of instant and a cup of freshly ground brew.
This video actually proves my point. James not only avoids tasting the coffees blind, but you can see that at 6:35 the particle volume is all basically the same size with extremely minute differences - looks like a factor of less than 10% volume density with very little distribution difference between grinders.
The size and consistency of the ground coffee makes a huge difference in extraction of coffee and therefor the taste, so a grinder that can make a consistent, repeatable grind will be noticeable (perhaps not as noticable as purchased ground vs freshly ground), but for some the difference between instant, and fresh ground with a $50, $500, or $3000 isn't worth the price.
$50 vs $500 Vs $500,000 Coffee Grinder: https://www.youtube.com/watch?v=WkYqHWThIpA