I might be wrong, but I think the original commenter was more or less stating this, but just in a different manner.
The fact that a $1 change in a $800 stock has the same effect as a $1 change in a $30 stock is because the index is price-weighted. This is arguably not a good measure of the overall behavior since it ignores the market cap. (Which I believe was your point)
A market-cap weighted index (like the S&P 500) would overcome these issues.
Comments
I might be wrong, but I think the original commenter was more or less stating this, but just in a different manner.
The fact that a $1 change in a $800 stock has the same effect as a $1 change in a $30 stock is because the index is price-weighted. This is arguably not a good measure of the overall behavior since it ignores the market cap. (Which I believe was your point)
A market-cap weighted index (like the S&P 500) would overcome these issues.