To keep costs, down, make sure that you do not enter the Swiss motorway system (signs are in green). Hence, in case you are renting a car in Geneva, make your way across to Chamonix in France, where you can enter the loop. Once on the loop, avoiding toll roads should be straightforward, as the road to and from Martigny goes along minor roads; otherwise it is 40 Swiss Francs for the vignette (or 50€ if you do not have that currency at hand). In Italy, you can save a little over 25€ by setting your Satnav to avoid the tolls on the Italian Autostrade system, although this will add a good 2 ½ hours to your journey. In France, you can save around 10€ but the additional journey time will be around 1 hour.