Maryland just opened the new four lane, 1.7 mile Harry Nice Bridge across the lower Potomac about a year ago. It is somewhat similar to the Francis Scott Key Bridge as it has to accommodate ship traffic under it. I haven’t found the final total cost, but I think it came in under $1b, not including demo of the old bridge it replaced. Construction started in 2019, if memory serves me right. Triple the cost and you probably have the cost for the replacement of the FSK Bridge given it will need to have a longer clear span over the shipping channel and extra protection for the piers.