Item Value List vs Item Movement History Report (including cost)

I have been trying to create reports for previous points in time, but I am so confused at this point as to what is what. I've ran an Item Value list, which shows the current value of items, and got an extended cost. Then I ran an Item Movement History Report that includes cost with a filter that begins before the store opened and ends today. The extended cost in this report was very close, but not the same as the extended cost in the Item Value list. Is there something that the Item Movement History Report takes into account that the Item Value list doesn't, or vise versa? Because logically, to me, they seem like they should contain the same value, given the filter values.