I just know about LeHavre, France. We will be there for one day about cruise ship in Sept. I too have been told shore excursions are very expensive here. Transport to Paris is $70-$100 each. There is a train, but it leaves at 7:55Am or not again until 10AM. It is 2 hours by train to Paris, a bus takes 3 hours or more. There is a taxi service that will do a 10 hour tour for around $90 ea., but they do not take reservations, so you can only hope to do this. The only other way is to get a rental car. Avis is in town, but I was told you do not want to drive in Paris. So you leave the car on the outskirts and take a train into town. None of the above is very good. We still haven't decided what we will do.
Let me know what you decide. Hope this helps somewhat.