I spend about £175 altogether on my 17 year old and 8 year old, all presents included, and then another ~£95 on my eldest, her husband and both my grandchildren (who are both under 2). So £250 for all 6 of the immediate family. It's a lot and I have to really save for it, but I can manage it and it's certainly not more than I can afford. I would never consider going into any debt for christmas or giving up anything essential/important to afford it.
For my kids, I am trying to explain splitting money, but my 17 year old (learning disability, FASD and many other issues) doesn't understand money and works on what she can see not what she's been told - so I don't actually spend the money evenly on them both. I split the presents evenly instead. They have nearly the same number of presents and no one has anything huge to themselves - eg. if I'm buying some train track as a main present and it comes in a big box, I'll mark it for them both, not just for DS, even though he's the one who'll actually use it most of the time, just because 17 year old can't cope with seeing someone else get a massive (in size terms) present, even if she's surrounded by load of smaller ones. So this year I'm doing the same, I won't split the money exactly evenly, but on the day no one will be able to say "she/he has way more presents than me/bigger presents than me"
As for the xbox - no flipping way, as others have said, the pre-orders have already sold out so you'd be spending like £5-600+ on it, and that, in my opinion, is absolutely insane.