Identify Any Fallacies in the Following Passage Either by Naming

Short Answer

Identify any fallacies in the following passage either by naming them or, where they seem not to conform to any of the patterns described in the text, by giving a brief explanation of why the fallacious reasoning is irrelevant to the point at issue.
You're worried that the very expensive diamond you want to purchase may not be worth the price, and the salesperson says: "We know diamonds here and we've examined this one very carefully. You can rest assured that it's worth every penny."