Here you go http://www.aena.es/csee/Satellite?Language=EN_GB&pagename=subHome&MO=1&SMO=2&SiteName=VLC&c=Page&cid=1048790574469
€14.40/day up to four days.
The last time we went in June, the toll was about €12 each way but that was getting on and off at Junc 42 just past Ulldecona.  That's probably acouple of miles less than using J41 at Tortosa.  Wouldn't have thought the time would be much different either.