The seller that is defrauding the buyer will follow several steps.
You should learn these steps, so you won't be defrauded like this
1) List all items individually
Any buyer foolish enough to bid on multiple auctions from the same seller has selected themselves as the target for fraud.
Example: Lets say you are listing 20 related books in a series. Instead of listing them as one big batch, list each of them individually. Each will have a minimum shipping cost. Since these are books, we will say shipping cost is $3.17 each for Media Mail, but the seller may feel free to make it higher for no reason. Next, lets assume one buyer wins 8 auctions, while the other auctions go individually or in lots of two. The seller won't be able to defraud anyone significantly on small lots, but the 8 lot winner has a total shipping charge of $25.36.
DEFEATING IT: Never bid on more than 1 auction by the same gouging seller. A gouging seller will usually ignore your communication regarding combining shipping, so they can claim ignorance afterward. This is a key tell.
2) When shipping is totalled offer a discount
Next, offer your buyer a small shipping discount on the invoice you send. This serves two useful purposes. First, it implies to the buyer that you are reasonable and will work with them, when the opposite is true. More importantly, this prevents your buyer from leaving feedback in the DSRs on the shipping and handling price, automatically leaving 5 stars in that part, because of the discount (despite the massive fraudulent overcharge!)!
Example: Continuing from above: The 8 lot winner has a total shipping charge of $25.36. Offer a shipping discount of $10. This leaves a total shipping fee paid of $15.26. The actual shipping cost, for Media Mail, and with the eBay discount, comes out to about $7. You pocket the remaining $8.26 of pure (fraudulent) profit, and the best part is you get automatic 5 Stars on your DSR's for shipping price! The buyer can't even do anything about it!
DEFEATING IT: Do not pay. Let them file their non-paying bidder complaints. Until the shipping charge is what it should be, do not pay. Once you pay, you are hooked, landed, and skinned, and your money is gone. Deal with it.
3) The buyer will probably contact you when he/she realizes that you are defrauding them by charging more than double the actual shipping cost. Your goal is to get the buyer to state that if you do not refund the amount you are defrauding them by, they will leave negative feedback telling the truth about your fraud. This is easier to do than it sounds, because of absurd notions some people have about "justice". Once the buyer has then left negative feedback, your fraud is nearly complete. You complain to eBay about "Feedback Extortion" and eBay will remove the negative feedback accurately describing exactly what you did to the buyer.
Once eBay removes feedback, it can never be re-instated, and the buyer can never leave feedback for those transactions.
Thus, none of your future buyers will know that you will defraud them in exactly the same manner!
Example: The buyer contacts you, saying something like "A $15.26 shipping charge seems unreasonable for something that costs $7 to ship. You will send a refund, right?" You state that the money you are defrauding them of is a special handling charge. They will probably respond remarking on the absurdity of the statement (especially with all that work you saved them by shipping one package instead of eight) and state they will leave accurate and truthful feedback on your account about what you did. Once they do this, you have won. When they leave negative feedback, describing exactly what you did, complain to eBay about "feedback extortion", and the accurate and truthful feedback will be removed!
DEFEATING IT: Do not ever mention the work "feedback" to a seller. Not EVER! If you even think about using the word "feedback", your seller is setting you up, and you should respond accordingly, usually with a complete return.
-The first step in defrauding the buyer by gouging on shipping is to offer multiple auctions and make no statements about combining shipping. Ignore any messages sent about the subject of combined shipping, and pretend ignorance afterward.
AVOIDING FRAUD: Bid on only 1 auction at a time, for a seller that engages in gouging shipping prices. Probe the seller to discover if they intend to gouge their buyers on shipping. Silence means they will gouge you.
-The second step is combining shipping and applying a small shipping discount, much smaller than the exact shipping price would merit. You will get automatic 5 stars on the shipping price DSRs even though you defrauded your buyer by charging more than double the actual shipping.
AVOIDING FRAUD: Do not pay. Take the non-paying bidder hit, unless the seller updates the invoice for exact shipping.
-The third step is to get the buyer to mention something about negative feedback. Once they do this, your fraud is complete and you are free and clear. After the buyer does this, contact eBay, they will remove the negative feedback, the buyer will be unable to do anything, and your future targets will not be warned.
AVOIDING FRAUD: Never mention feedback, and immediately return the parcel for full cost plus full shipping.
Lastly, eBay and Paypal know about these things, and will do nothing about it if you are defrauded in this way. I discovered this after 3 hours on the phone with their useless customer service departments. The steps outlined above are your only recourse.
Hopefully this helps you avoid fraudulent sellers.
woe be to him that defies the tree,
for he shall be cast out into the world
through the veils of pain and fire