The price is wildly out of date but apparently there's 3 or 4 peajes and roughly 1200 each one, except the Illia which is 2200/3000 offpeak/peak.
You don't have to use the Illia either.
https://www.gorfhi.ar/Precio-De-Peaje/De-Buenos%20Aires-Buenos%20Aires-A-Rosario-Santa%20Fe