@veruca_boi,

I truly don't think it's anyone's business why a seller sets a particular price for the items price or for the postage charge. I cannot imagine getting onto the phone with DJ and asking why the postage price is $xx. I certainly wouldn't expect the DJ customer service representative to tell me, or to break down the components of the cost.

If I were a seller on eBay, and a potential buyer asked me "Why are you charging $x for this item?" or "Why is your postage cost $x?" or even "Why are you charging $x for postage when [other seller username] is only charging $x?", I'd have a polite reply ready to go.

"Thank you for your enquiry. Our prices are set based upon a number of factors. You are more than welcome to purchase multiples or a variety of our items and take advantage of our combined postage discounts. Best regards, [name]."

If a potential buyer persisted, it might be indicative of that person's being a high maintenance buyer, and hence best placed on one's Blocked Buyer List.