A fairly infrequent traveller here. The CFF website says thar, in addition to the rail journey a City Ticket gives me a day ticket in Geneva.
Does that mean it would cover a Journey Nyon-Geneva Cornavin-Bus Stop- Geneva Cornavin?
It seems it should but if I ask for a Round Trip City Ticket it’s double the one way price. Shouldn’t it be a one way city ticket price plus a one way Geneva-Nyon ticket?
If you enter your trip to geneva then you can add the city ticket for whichever city you want before buying the ticket. should be 4.5+4.5 for train +4 geneva ticket = 13 CHF with half price, 24 full price. The city ticket is nothing else than a normal day ticket of the local network but maybe discounted.
Unless you're making multiple trips within Geneva (generally more than 3) then the city ticket isn't worth it. You're better off getting a ticket to Geneva and then Unireso tickets to cover your travel in Geneva.
The Easyride app which is built into the CFF app makes a fairly good job of calculating the optimum fare. It certainly is much better than the CFF ticketing app or the CFF ticket machines themselves, which will always try and sell you a city ticket.