source: The original plan for the bridge was to use concrete to keep costs down, but a steel design was chosen after the bids for a concrete bridge came in too high.
target: The original plan for the bridge was to use concrete. Concrete keeps costs down. A steel design was chosen after the bids for the concrete bridge came in too high.
references: The original plan for the bridge was to use concrete. Concrete keeps costs down. A steel design was chosen after the bids for the concrete bridge came in too high.