You might need sample language to explain your mistake to buyers. Here is what Amazon just emailed me about an order I placed two months ago:
We’re contacting you about order #114-0405100-298xxxx. We recently discovered an error that caused the following item(s) to be displayed at an incorrect price:
[Description of Item]
In this case, we’re unable to offer this item for the incorrectly posted price. Therefore, we’ve cancelled your order for this item, and you haven’t been charged.
At any given time, despite our best efforts, a small number of the millions of items on our site may be mispriced. We’re very sorry for any disappointment this may cause.
We value your business and hope to see you again soon.