Try co-operative on line holidays and try to do a late deal which will save money.
Equity (might be Rocketski now?) specialise in all inclusive family holidays and go to smaller resorts, you should easily get below 4K with them.
Skitopia do even cheaper holidays, they tend to specialise in school trips so the accomodation can be very basic, that said I have gotten some very cheap holidays from them. They do Serre Chevalier which is a pretty decent resort.
Half term in a catered chalet will be the most expensive option out there, if you want much cheaper you would be better either HB in a hotel or self catering/ B&B.
It is worthwhile spending a fair bit of time on the net, teletext, on the phone trying to get the best deal, it will save you thousands though I assure you.
Also use the forum on the website “snowheads”, they are very helpful on best locations, ski schools, weather reports etc.
Best of luck :-)