Interesting look at things.
There's a few points that don't make sense to me.
If the price analysis is for commons the average price for each grade should be for commons. If it is I want to know just who is buying 2s for $50+ so I can send them most of mine.
Without breaking out commons from HOF and high demand cards the numbers don't seem to mean as much. Overall, the price of PSA commons in low grade could be lower and the HOF prices higher. In general, HOF players and other high demand cards tend to be graded roughly twice as often as commons.
It's interesting that PSA6 cards are off about 3% while 5s are up by about 5-6%. Leaving the percentages off the PSA chart seems a bit misleading.
Another interesting thing is that the difference between companies is a lot more in higher grades. I think that can be solidly explained by the popularity of the registry. (Also odd to me since actually "competing" would be pretty expensive just to get into the current top 25. If someone is overspending to shoot for 50th, good luck to them but I just don't see the point)
The differences in grades 4 and under don't seem significant. I don't know statistics well enough to figure out the deviations and whether they're big enough to matter.
Steve B