I’ve provided a reference to a paper below which looks into the calculation of possible costs. It doesn’t provide something where you could insert measurable things – length of tramway, number and cost of trams and so on – and multiply them by a cost read from the paper, but provides reference to what needs to be considered. Table 1 provides information about the costs of tramways built up as far as 2004. Hope this will be of some use and gives an idea of where and how to start doing a study focused on a specific project.
(David Walmsley – Transport Analyst BSc – PhD, CMILT, MCIHT, tram technical lead. Member of UKTram; UK Rep on European Urban Tram Forum; formerly Fixed Track Executive at Confederation of Passenger Transport)