11% for the least expensive auction listing. When you add reserves or stuff like border, bold, featured, etc. it gets to be around 15% and even more if you list in two catagories.
Buyers snipe because the more bids and the more views and the more people that have it on their watch page, the higher up the search engines it goes. More exposure = more bids. For years I used the strategy of a buck auction style and let it rip and the above is the reason. Ever do a google and ebay stuff comes up? Thats one way it gets there.
So, as a buyer you are trying to get that item as cheaply as possible therefore you snipe. I have a sniper program and always use it but if I ask seller a question will always let them know I will be bidding.