We had a problem with material cost on one part when it's evo count went negative do to a PO receit that was not entered before we started shipping the product.  The most we had ever paid for the item was $28.01  We did have 3 negative sales at $72.72, so I would think the highest our cost should have gotten was $72.72.  When we went negative the 1st 10 went out at a cost of $28.67, the next 3@$120.61, 3@$577.19, 2@$1298.77, 4@1298.77, 14@1,298.77, 39@1298.77, 29@1298.77 AND 34@1,298.77.    
The total material cost error was $157,831.82.  What caused that items cost to keep getting larger?  Other than doing our receiving before we ship, how could that have been avoided?  We tried to correct the problem by running UT-K&H, but wound up just deleting all of the inventory and putting it back in at the correct cost and making a journal entry to fix material cost and sales.