I just had mine this weekend and got just over $500 in sales!
Only about 1/3 of the people I invited showed up (that's normal), but those that came had an average order of around $70 each.
People will buy more if they see the product. Invite three times the amount of people that you would like, because some won't show. Make pretty invitations to give them to make them feel special and personally invite them.
Have a lucky door prize to intice more people to come along and offer a free gift if they bring a friend (to increase numbers).
Keep it casual so people don't feel pressured and they will buy more.
It's not too late! Have an open house with all your Christmas products and you'll reap the Christmas rewards!