Let me elaborate on the shill bidding process and why ebay will NEVER step in and stop it:
Shill bidding is when a seller creates several different profiles and usernames, and when they post an auction, at some point they will use one of those different usernames to bid on their own auctions, thereby artificially raising the price.
There are several different ways to detect shill bidders, things that raise red flags, such as geographic location, and when looking up bidders and sellers' auctions if there are more than one auction of a particular seller that a certain bidder has bid on, and that a bidder hasn't bid on anything similar in other auctions.
If the auction is PRIVATE, you have no way whatsoever of detecting this kind of fraud. EBay CLAIMS it's illegal and against their policy, BUT... eBay's fees are based on what an item sells for, meaning no matter who bids on it eBay makes more dinero, so it's not in their best interest to curb shill bidding.
In the past, I've reported instances of OBVIOUS shill bidding, and they've done little if nothing at all, and frankly even if they actually cancelled a user's account, it's not the hardest thing in the world for anyone to set up another one.
Just so you know what kind of people are out there on eBay: There was one instance where I was looking for a car a few months ago, and I tried emailing a seller to look one car over, (they didn't put a phone number or any other contact info,) and when I got no response, I did some digging and found their photos hosted by an external website... as well as 5 other eBay usernames using the same website. When I did a WHOIS on that website, I googled the registered owner's name, and found out said owner was CONVICTED of rolling back odometers on 75 cars in the state of Pennsylvania, and yet he was shill bidding on all of his automobile auctions.
Ebay did NOTHING when I contacted them about it.
Caveat Emptor.