You will only win the auction by the amount needed to win. If you bid $50 on an item whose next highest bid is $25, then you will win for $26.50, the next highest bid increment.
AS simply places your bid at the last second and eBay does the rest, just as they do when you bid manually. In answer to your question, if you are already the high bidder when the auction closes, then your bid amount will not change. Auction Sniper will, however, charge you their small fee for the snipe, even though you were already high bidder, because they still had to do the work for you.
You will only win the auction by the amount needed to win. If you bid $50 on an item whose next highest bid is $25, then you will win for $26.50, the next highest bid increment.
You will only win the auction by the amount needed to win. If you bid $50 on an item whose next highest bid is $25, then you will win for $26.50, the next highest bid increment.