Hello Fati
There is indeed an inconsistency in the ticketing system, and I identified the cause. When you purchase the Saver Day Pass through the shop function (without entering a route), the ticketing system calculates a half fare Saver Day Pass for the child, while a Children Day Pass would be totally sufficient.
I will report the case to SBB.
My advice: purchase the tickets by entering a route and choosing ‘single and return’ option. The total cost of CHF 141 is correct: 2 x Saver Day Passes, 1 x Children Day Pass. The baby does not need a ticket at all.
Kind regards,
Roland