Upgrading ticket to first class

hello,
let me begin by saying how much help this forum has been in shaping my itinery,i would be buying a swiss saver pass for 15 days, but for long trips like zurich to lugano which is zbout 3 hrs i would like to know if i upgrade to first class, how much extrs would i be paying for the first class ticket with my second class saver pass.....awaiting your esteemed reply