I think very few people will be able to tell the difference.

However, IMHO, the source of the beef can trump all that. I used to buy a year's worth of beef from a local farmer all at once. Even after a year in the freezer, a burger made from his grass-fed beef tasted better than one made from meat bought from the grocery the same day. When you start out with high quality meat, it takes a long time before the flavor degrades.

OTOH, "regular" store bought ground beef tastes nasty after being frozen for a few months.

I haven't seen such a chart, but I don't know of any burger restaurant that grinds a la minute - not at any price point.

That's a moot point if you can't tell the difference or if the one that was pre-ground ends up tasting better in a blind taste test. I agree, however, that the freshly ground one should taste better.

My point is that even high end restaurants haven't found it worthwhile to grind immediately before cooking, so it's probably a pretty minor difference

Probably because it's labor intensive, something an automated machine can handle just fine.