Gronk,
That sounds like potentially very good advice. The only questions are when and why? Would you do it as quickly as after the second email exchange? Would you do it over a mistake that your company had made? And would you do it over $13?
I posted this precisely because I wanted to get other people's input, to insure some measure of objectivity.
In this regard, Knife Outlet's post really stuck with me. I am grateful for his providing some insider information about the business and the slim profit margins on which it often operates. That said, if I were running a business in which $13 was a live-or-die sum of money, I would concentrate on making sure MY OWN employees did not screw up orders that cost me more than $13, rather than potentially losing customers over the $13 once MY OWN employees had already screwed up. The invoice that was sent to me has the correct item on it. The item that was shipped to me has a completely different shape/look/tag, and any semi-competent employee who knew anything about the business would not have shipped it to me. My point is this, train your employees not to provide bad service in the first place; do not pass this burden on to your customers, particularly if your rationale is going to be how these little mistakes cost you so much and are really unbearable considering the conditions under which you operate.
IMHO,
John