In reply to TheFasting:
Agree with everyone else that lifts should be the last thing you cut out of your budget. Yes they're expensive, but they can save you *so* much time and effort. There may well be people out there who have a long term pass and 'rent' it out for cheaper than you would pay officially. It's not allowed, and they have a photos on them, but a lot of people seem to get away with it. Ask around when you're there, or on chamsocial.com
Getting there and around can be done by hitching if you have the time, although cheap(ish) flights might make more sense, especially from Norway. Free travel up and down the valley on trains and buses (I think) with a guest card you can get from a campsite. When we stayed in the one in Argentiere, we only paid for a couple of nights, but the travel card was valid as long as we wanted.
Stay off the booze if you want to save cash, but save something for a celebratory drink or meal after your epic ascent. It will taste wonderful.
You can bivvy in the mountains. Officially dusk till dawn, then take it down and stash it somewhere out of sight. Don't make a nuisance of yourself, and try not to do it too close to the huts, even though you will see others doing both.
Supermarkets are a bit more expensive in Cham. If you're passing the big one in St Gervais-les-bains, it's worth stocking up there. But don't go out of your way.