I think the "cost" goes up as they get older - we have probably spent about £60 so far, but no stocking fillers yet (surprisingly expensive) on DD, not actually bought very much with our money mind! She is only four so actually pretty easy, no requests for playsttions, wii's etc, but am bracing myself for that to start soon.
My eldest DD has cost us a fortune over the years. She is 19 now and left home - I keep asking her what she wants, she just says, "oh there is nothing i want" um, well that is because her DP is probably going to indulge her yet again, im typing on her cast off lap top that he bought her two years ago - it was a DS last year, this year an iphone!! Lucky girl - and lucky us else we would have been getting those impossible requests. I think the most we ever spent was £400 on a guitar and amp - you know, she used it about three times , its upstairs with broken strings!!!
I'm also very lucky to have a very generous mum who gave us £150 to go and splash on DD2 the other day - we were like we wont be able to spend that! oh yeah?? Two shops, ten minutes = gone!!! For our money we bought some lego sets (good value for money and will last) and the super indulgent pressie of this year - a buiscit the dog, fur real animatronic puppy, its amazing, but came with a £100 price ticket - i was but actually coudlnt contain myself when we bought it - it actually cost more than our actual dog!!! but it is just soooooooo cool!
We are actually quite broke this year (again!!!) so wont be buying each other any presents so our total spend of our own money on xmas presents will probably be about £150 for both DDs. Will be miserly scrooges and not be doing neices and nephews this year. Will do my friends baby and thats it.