TCO calculation mistake when going from Lotus Notes to Outlook365

Companies are moving from Lotus Notes to Office 365, and one of costs that are not taken into account when business case is done is the use of the network in the new situation (TO-BE). This information is key for the TCO calculation.

I had the opportunity to discuss informally with three different of my colleagues and they recognized me that the monthly expenditure due to band witdh consumption has increased, that they also had to increase the available bandwidth contract, and hence to increase the secundary lines (back-up).

I know, OPEX/CAPEX is not the only reason to get rid of Lotus Notes, but: This is a lot of money!