We missed Leon out last year and went up the side of the Rhone stopping for a swim and an ice lolly thinking it would miss out some tolls too, when we checked it made no difference.
Its £80 tolls and £80 fuel each way in simple terms.
The drive avoiding them is hard going, stick an extra person in the car!
Its def better value if camping, if going with holiday co then if fly if doing nothing else, it just makes life easier.
Tunnell makes a difference too, time the ferry wrong and it can take near 5 hours to cross.
Buy fuel and food off the motorway, have a look where carrefours are first or just come off when you kee a mid size town, motorway fuel gets expensive when your burning a lot!
The drive home is the worst, factor in a stop for the night as you will be knackerd. Ride all day, pack and drive till 10ish, get up and get a early afternoon crossing getting you back late evening.