PO Cost Update Error

System is automatically populating PO Cost but won't let me update the cost.For POSTE2522403-1 the PO Cost was calculated as $33810.00 - which is wrong. I tried to update with the correct amount and received an error saying PO Cost can't be less than previously saved cost. There should be no constraints on the amount we enter. We haven't updated MBC to let it do automatic calculations of price and really don't know if we'll ever do that. Please allow us to enter whatever we want in this field. Thank you.