If the seller feels he is being harmed by bidding manipulation, like described in this thread, he should cancel the auction if he has time. First he should cancel all open bids and then end the auction early. EBay provides for this in it's rules:
"Stop the Auction!
You may miss out on just the bid you've been waiting for if you end your auction early. Still, there
may be times when you have a valid reason to end an auction. You may stop your auction when you
decide not to sell. To do this, you must cancel all bids on your auction before it ends. If you
do not do this, you are obligated to sell to the high bidder"

If you do this, I believe there won't be any final value fee.

If this manipulation is done at the last moment, so you don't have time to cancel the bids and auction, I think the seller should refuse to sell the item. He should complain to eBay and have the fees cancelled. (For example, a group of conspirator bidders early on bid the item way up, scaring off potential legitimate bidders. Then minutes or seconds before the close of the auction, they cancel the high bids, leaving one of their group as the low-bid winner. In situations like this the seller should refuse to sell the item at the winning low price.)

Robert