We are traveling on a Sunday from CDG airport to Rouen in June. I am trying to compare the cost and complexity between the two modes of transportation. I am assuming by train SNCF would be the most economical, but having a difficult time trying to understand the itinerary and can not seem to find the total cost with all the transfers. I got quotes for a hired driver from $210-300. There are three of us traveling. Please, any help or suggestions would be appreciated.
About 20 years ago we had to get a taxi from Rouen to Paris, due to a train strike, so as to catch our flight back to Canada. The cost was 1000 francs, which at that time was $300CAD. If you are getting quotes 20 years later of $300, go for it, especially since it will be divided among three of you, if only for the convenience and pleasure.
I picked a random day in June --June 12. Tickets from St. Lazare to Rouen were 10 Euro each. It will cost 50 Euro for a cab from CDG to St. Lazare. The rule of thumb is to leave 4 hours between ETA and a train from Paris. This gives you a little cushion for slow immigration/passport control, luggage and the trip into town. So it looks like it would cost about 80 Euro to make this trip if you book ahead on the train. Use only the official taxi queue; don't be deflected to another line or to a cab offer. St. Lazare has plenty of shops to buy lunch for the train or to have lunch before travel if you have extra time.
The rail site I use to purchase French rail tickets is https://www.oui.sncf/ (who knows why they chose this branding, but it's the official SNCF ticketing site).
There are no good routes from CDG airport to Rouen directly; you will have to go into Paris to make this rail connection. (If you search for direct CDG-Rouen tickets, you get routings via places like Lille, which is an incredible detour out of your way.) As janettravels44 mentions, there are plenty of €10/person tickets available in June; I checked the first Sunday 2 June and there were plenty of them available.
Since you are three, a €50 flat-fare cab from CDG to St-Lazare is probably the easiest. If you had been a solo traveler, I would have recommended the RER as an economical alternative: you would take the RER B from CDG to Gare du Nord, then switch to the RER E and take it one stop from Magenta to Haussmann–St-Lazare. However, since this would be €10.30/person and there are three of you, a cab offers a one-shot easier trip for a €20 premium.
If you can get a car to take you directly to your hotel for a bit over $200, I would be inclined to do that. Taking 2 trains ( or a taxi and a train) to get to Rouen and still having to get from the train station to your lodging, to me makes the car a good value.