Well, I'm a European bookseller, and auctions in my line of business usually cost 25-30 % over the auction price. Also, shipping is more because of the weight. 33% however, I think is rather steep. Coin auctions cost 12-20 % extra, to me that's cheap.
I bought some coins with CNG, and the upcost is something like 15-17 %, plus shipping to Europe is about 35 dollars. At Pecunem (Gitbud, that's Germany), the cost is 11,9 % and shipping by Fedex 10 euros. They must have a very good contract with Fedex, for when I use that shipper, it is very safe but the cost is ten times higher. Naturally, Ebay doesn't take cost at the buyer's side, but you are much on your own in risks of fakes and other problems. Therefore, I am using trusted sellers I know. As a bookseller, I have a small numismatic section in our website, don't know if I'm allowed to post it here, but this is it: https://fokas.nl/numismatica/ (Now you understand why I'm specially interested in the Byzantine emperor Phocas)
I'm think you mean Direct Debits - or possibly bank transfer? All our bills are paid by direct debit.
Perhaps. I still bank with HSBC UK and USA. They had a term that was common enough that Barclays, Bank of Scotland, etc used. I just do not remember, sorry.