i adjusted all serial numbers out of our inventory for a specific item but for some reason the average cost of the item is not 0. Where is that average cost coming from if there is no inventory ?

Check your Inventory Costing preferences. Depending on the setting, the costing engine might still need to run. This may then clear out the remainder. At worst, check back on it tomorrow. If there's still an issue then you can open a case with NetSuite to see if they can explain any remaining variance. You can read more about inventory costing here: Suite Answer 28092

thank you