This depends heavily on the density of operation; globally at least for heavily used lines the total cost of operation (infrastructure, locomotion, etc.) is muc

This depends heavily on the density of operation; globally at least for heavily used lines the total cost of operation (infrastructure, locomotion, etc.) is much lower for electrified lines, in no small part because each locomotive needs much less maintenance. From that regard, it's somewhat surprising that none of the busiest lines have been electrified.