I don't think the people bidding on this auction are the type who want to get involved in market manipulation, or not at least for this tiny amount of money. Also I don't think the amounts involved are big enough to warrant market manipulation. It might not even be profitable let alone worth the risk of committing a crime.
Since when bitcoin market manipulation considered as crime? (and by whom?

)
typically manipulation of any market is a crime. Even if it is not yet in bitcoin, these particular players probably wouldn't want to risk it. Even if it is just something that looks bad later they wouldn't want it. They have bigger things to worry about than saving $100,000 or whatever on their bitcoin purchase.