Currently, when you receive a buyorder, you can approve it after making changes to the line items (i.e. prices).
The customer gets an email to list out what the prices you offered them were.
The members do not get a copy of this email.
This means that later on, if the customer were to dispute the prices on the buylist and (not that they would, but there is nothing to prevent them from changing the prices on the approved buylist email to a higher value), there is no 'sent email' for the member to review what the prices were originally given to the customer to counter their claims.
In general though, being able to keep a track of all sent buyorder emails to the customers would be extremely useful for audit purposes
