The information on this is great. Appreciate the effort.
That said, given the sheer amount of gold that can be had/obtained in just EA Act 1 alone, I can careless about my charisma and how it effects my buying or selling prices.
You can turn a trader/merchant green (friendly instead of neutral) though, but again, have not tested or cared enough to test what effect turning a trader/merchant friendly has on buying and selling prices, again, given the sheer amount of gold one can accumulate in just EA Act 1.