Some things you can do to help keep the costs down...(if you're not on apckage that includes all this).
1) TK Maxx does have cheap gear. Salopettes, trousers, jackets, gloves etc. In some places you can get by with thermal pants, tracky bottoms and waterproof trousers, but I wouldn't recomend it in most places. Tesco are apparently launching their own skiwear, and Decathlon have some pretty cheap stuff.
2) It can work out cheaper to buy your gear rather than rent it if you're going for two weeks. You can pick up 2nd hand stuff, or go somewhere like Decathlon (here you can pick up a snowboard for 80 euros). Obviously the costs mount up, so you'd have to make sure you were getting it cheap.
3) Some resorts in the Alps have free lift passes for kids. I'll try and check which these are. That will save a lot of money. Others will do deals if you book in advance, or for a certain block of time. Also if you're not an early riser half/day or late start passes are cheaper. But remember lots of pistes and lifts start shutting at about 4pm.
4) Think about the transfer from airport to resort. Some can be reached on public transport, some from airports like Milan, Venice, Barcelona etc, which a) have budget flights and b) aren't neccesarily more expensive during ski season.
But, it will end up pretty expensive regardless. A package is probably the way to go...