As for maintenance costs, I imagine that one can expect a very substantial decrease due to the use of CAD, better materials and improved practices. Cost reductions of >40% per flight hour were achieved in the military for "equivalent" aircraft between 1970's and 2000's, and reductions of >50% per seat-mile were achieved in the same period for commercial aircraft (eg: early B747 vs B777). Maintenance costs for commercial airlines are a fraction of the fuel costs in any case.
Finally, it is worth remembering that the Concorde was a very profitable business for British Airways, with operating profit of ~40% for the Concorde!