Everyone is overlooking the most important cost and that's downtime cost. Just yesterday one of the network guys made a configuration change that took the whole data center offline for about 30 minutes before he could get to the data center to get console access and revert back the changes. If we had Juniper at the core with the "commit confirmed" automatic config rollback feature it would've reduced the downtime to within a few minutes instead of 30 minutes and the config checking feature could be used to prevent future occurrences.