The reason you don't use JE for this, is that you orphaned the Items by Name from their Value in that account.
Adjusting inventory is done Per item Name, specifically, for that item.
Why are you reducing Cost? Cost is your basis, or what you paid. You don't change that, later.
"We are doing this for year end adjustments to inventory cost. We may be selling these items in the future, so I assume that profit would be 100%"
If they are telling you to Write Off the cost as expense, already, then ask them why are you having to manage it as Inventory, then? You don't need to use Inventory Management in QB, to track "stuff."