For pure toys this year its going to be about $400. the biggies are an a Itouch or DS, a lego city set and the Mario Winter Games for Wii.
However he will also get books (we give him a world almanac ever year), small (think $2-$5) gifts for his stocking, some candy.
As a tradition he will also get new jammies
on christmas eve.
The other thing we do is not get any new clothes in the fall (no "back to school" shopping since it stays warm for quite a while) so under the tree he will also find socks, underwear, a new winter coat (if last years doesn't fit) and any other clothes he might need.
So all in all I probably spend $600 but since we buy basically nothing in Aug thru Dec it averages out to be just over $100 a month which as % to total income is not a lot.
I have christmas account that I add to all year long so no credit card debt for us. This account covers all christmas presents (son, husband and homemade gifts for family/friends), nanny bonus and gift, teacher gifts and about $200 bucks for the family we "adopt" each year. It also covers the big holiday meal. In January I will go thru all the receipts and then come up with next years budget. I put the $$ in a high interest saving account as every dollar counts! This year I might have some xtra leftover which is always a nice surprise.