Originally Posted by david7031

The general, everyday, walk-up fare (2nd class) from Basel to Zürich is CHF 15.50, which is $17.56 as of this minute. This is valid for all trains, express or local. For these normal tickets, there is no price difference for the type of train. (Unlike Germany, where the ICE is much more expensive.)

SBB is offering capacity-controlled, last-minute fares through mid-August on many Swiss conncections, including Basel to Zürich, where the lowest possible fare is CHF 6.20. (Although looking at 3 example dates in June, I saw no fares less than CHF 9.00) These fare can be booked on-line a maximum of 14 days in advance. For the dates that I looked at, there were only 5 or 6 connections offered.

If saving $5-10 per person is super important to you, you can look into these "Sparbillet" fares starting 14 days before your trip. Otherwise, just pay the normal fare and be done with it!