But more importantly, the opportunity cost of delaying may be exorbitant. If documents are posted to a Web server, so that they are securely accessible to any authorized person with a Web connection and a browser, you may be able to cut your courier bill by half or more. Those savings alone will probably suffice to justify the cost of an extranet. But there's much more. Consider that the number of communication paths in any network is roughly proportionate to the square of the number of nodes.
All communication flows through the switchboard.
This provides a permanent record to which you can refer later. It reduces the number of communication paths to only one more than the number of nodes. You don't need a degree in operations research to see that reducing the number of communication paths will reduce the number of communication errors, all else being equal. That is why I believe an extranet needs no detailed cost-justification any more than a telephone system needs one. You still want to select the best phone system for your needs, at the best price.