I think it's also important to remember that every family has its own traditions for celebrating holidays. Unfortunately, you can't control how the family next door is choosing to celebrate Christmas and the Santa tradition. If you're concerned about your children being exposed at your neighbor's house to traditions you don't approve of (such as a volume of gift giving that you think is "extremely excessive"), you may have to consider not allowing your children to be at that home, and instead host play dates with those children at your home.
Alternatively, you might alter your Santa story to explain or accommodate the inevitable inequity of gift delivery (not every home across the world gets the same volume of presents from Santa). One possible story adaptation might include negotiations/discussions between Santa and a child's parents, to ensure that the quantity of gift giving matches the values that the parents wishes to instill in their children (such as focusing on giving during the holidays, rather than receiving; or maintaining order in the home and encouraging imagination by keeping toys and electronics to a minimum, etc.). Hopefully others will have some additional creative suggestions for you too, if this is the approach you choose for handling the inequity.
Good luck -- I hope these suggestions are helpful to you.