We are trying to determine if buying a Eurail Pass makes sense . I cannot get a fare price for these trains (just a schedule) from the Bahn.de website. Any help would be appreciated.
Try the Swiss and French rail sites, rail.ch (or sbb.ch) and tgv-europe.com. SBB is showing full fare of 153 CHF and a discounted fare of 123 CHF, which may or may not be available for your date of travel. I would check tgv-Europe and compare.
Couldn't resist looking at TGV-europe as well. They are showing a "piccolo fare" of 71,80 euro for an earlier train that same random day I picked. One would have to depart Paris around 6:30 am to get that fare.