We Sell On Ebay alot, and just because its a low bid doesnt mean you can expect it. They may not "bump" the price, but 100 dollars is just to get the bidding started. Get a bunch of people fighting for it while its low, it goes up fast, dropping others out until the one thats willing to pay the most pulls through.
$100 is just go get attention, if it did end up "selling" for $100, the person would only have to have a friend bid either A: the price they want because of the chance of someone seeing it, or B: an outrageous price so they dont have to sell it.
Bumping hardly occurs anymore, Ebay is very strict about it.