I believe it is a problem with Lot and Serial items. Even the Count Card Variance Register is wrong. If there are multiple lots for the same item (i'm sure for serial numbers too), the Register uses the same lot cost for each item, instead of the actual lot cost. I've had to modify that report. You should review what each of the Serial Number unit costs are that print on the Variance Report, to see if they are the actual Serial Unit Costs in the Inventory tiers.