In reply to zimpara:
Couscous is generally cheap everywhere, wouldn't take that much of it with you, same with pasta.
Vegetarian food generally cheaper to make than meat stuff.
Bread is "expensive" to buy in France every day.
I tried walking in from the valley floor, when younger and fitter, we soon learned to use lifts but good luck
Wild camping is possible, just pack up in the morning and then head along to Les Gaillands to chill out
Buckets of wine way cheaper than drinking beer, avoid buying the "bargain" Panache, its not beer (as one of our party once found out)
When going high its also possible to "wild camp" as opposed to staying in huts, a lot of people seem to forget this - just watch out for any raids by the gendarmes!
When looking for a hostel don't stay in Cham, one of the other villages (a short bus ride away) will have cheaper hostels (and cheaper bars/supermarkets)
Don't forget to shower when you staying in a hostel, after a few days of camping/dossing and then walking/climbing you will need a shower
Have fun.