Family of four -- car rental

I think your estimate of a train to Paris of $600 is high. I took a train with my two daughters from Geneva to Paris for about $140, total. My daughters were 20 and thus eligible for a youth rate which seemed to be about half of the adult rate. I believe I purchased the tickets about 60 days in advance for saver rates. There are also Swiss Passes available. I used the Swiss Travel Pass but there are other options including a half fare card. Other people on the forum are very good at assisting in determine the best pass option. If you rent a car, you need to have a vignette which to my understanding is like a toll pass. Swiss trains are super clean, efficient, pretty much always on time and the views are pretty remarkable. If you want to experiment with train fares, good websites are loco2 and trainline.

The train ticket prices vary greatly based on how early you purchase them and WHERE you purchase them from. Basel -> Paris TGV Tickets can be had for a steal in advance. Avoid RailEurope as they inflate their prices and don't show you the full itinerary of available trains. Book either with that country's national train website (sbb.ch or sncf.com or bahn.de) or from a reputable 3rd party such as trainline.eu

Look for a trip from Lauterbrunnen to Paris with trainline.eu departing Lauterbrunnen 25 April shows me a price of 86Euro x 4 people = WAY less then your $600 train to Paris.

How experienced are you at European travel? Do you know about tolls driving through your countries of travel? Do you know about cross border drop-fees. Have you ever driven in Paris?

@Tim, additionally the teenagers can get youth tickets.

Are you certain that the $798 does not include a drop fee for leaving the car in a different country? Usually there is one, but it might be stated separately at the end.

How old are the teens? They may or may not be elegible for significant discounts, or even free travel in Switzerland on a Junior Card or Family Card.

Do you know how to find those discount fares Tim is talking about?

What type of transport do you contemplate using at Lauterbrunnen? High mountain lifts? You might definitely benefit from a Swiss pass of some type, especially if one or both teens are 15 or under (see question 2).

The cost of a Swiss Travel Pass is reduced for people under age 26. The French trains also have a discounted rate for those under 26. What I don't know is if single ticket purchases in Switzerland are discounted for young people. If you do not buy a Swiss pass product and teens are full price for single tickets, I would consider taking a Swiss train to the border to pick up a French train where rates are definitely less for young people.

Thank you all for your suggestions!
The kids are 15 and 17, so I've been entering their ages as I use the recommended sites [eurail et. al.] to find youth discounts; for the dates we need in June, $400 to $450 (for the four of us Lauterbrunnen to Paris) seems to be the norm.

Re: driving, We will have the car for our 4 days in southern Germany, have driven in major American cities (DC, NYC, Boston, etc.), but don't plan to drive in Paris as we would drop the car outside the city on arrival. [The car rental price already includes the drop fee, and estimating tolls, gas, parking, etc. brings the car to roughly $1000.]
I'm willing to pay somewhat more for trains as I would prefer a train from Laut. to Paris, but I was surprised how much more it will be.

I guess my revised question now would be: If we drop the car in Freiburg, Germany, and, four days later, take a train Laut. to Paris, what pass card/ ticket options do you all recommend for travel for those four days: Day 1 -- Freiburg to Lauterbrunnen, Day 2 -- hiking around Laut., Day 3 -- open to suggestions :), Day 4 -- hiking around Laut., [Day 5 -- train to Paris]?

I've read Rick Steves's pages on train travel, and (1) the two/three country passes provide more travel days than we need and are priced higher than point-to-point tickets would be; (2) We would still need some kind of separate pass for travel within Switzerland, right? I'm wondering if we just need point-to-point for each separate portion . . .

Again, thank you all for your help and patience; I'm feeling a little overwhelmed with planning the transportation for this portion of our trip.

Here is yet another option: We took a car into Switzerland from Germany and back as a family of four and it worked quite well for us - even saving money. The reason: the car allowed us to find accommodation off the beaten path too far from the next train station. But in a very picturesque location in the Emmental region (view of the Alpes from our rooms, cow bells as wake-up calls in the morning ...), central for daytrips and at under $100/night for a 2 bedroom apartment much cheaper than any options in the Lauterbrunnen area.

Will you be taking any of the (expensive) lifts such as going up the Schilthorn or Jungfrau ? If you're considering that, check out the Swiss half-price card which could lower your costs of the lifts as well as rail fares from/to the Swiss borders. With the Schilthorn, we broke even buying a HFC and using it for reduced fares Lausanne > Mürren > Lausanne.