I too have this problem.  I have an inventory item that I was charged $12.50 for 100 items.  But I actually paid $7.95.

I was thinking of a few possible options as a solution just now.  One, handling the situation with a (fake) credit memo for $12.50/100 items; and then re-entering the expense with the new dollar amount $7.95/100 items, though this too would be fake.  This would give me the corrected amount.I would just have to remember this when it comes time to balance the bank statement.  This should result in my only changing my dollar amounts and have my inventory item a wash... 100 out and then 100 back in.  ($12.50 out, $7.95 back in leaving a difference of $4.55 which I then have to watch for on my bank statement.)

I hope this works.  I think it will.  I too am tired of the ask your accountant questions with I, an accountant too, am having issues with trying to figure out workarounds for Quickbooks inadequacies.