You don't HAVE to pay tolls at all. You can work out a perfectly good non-toll route, and use that instead of paying tolls. You can get anywhere in the country, and on some routes you can almost get there as quickly as paying tolls. There are some fabulous non-toll autoroutes. We use the route Calais, Abbeville, Rouen, Chartes, Orleans via the N154, cross-country to Nevers, Moulins, Gannat, Clermont Ferrand, Beziers, and can do it without paying tolls at all. You can even avoid the toll for the Millau viaduct by going on the old road into Millau and then rejoining the A75 just a few miles further south.
You'll also save up to 20 centres a LITRE (not a gallon) by filling up in supermarkets or 24hr Express stations, rather than on the autoroutes.
However, you'll have to admit that the French do provide better facilities on the autoroutes for caravanners, with many more frequent places to stop.