Well if you buy something and on the listing it says MONEY BACK GUARANTEE, and you pay the buyers fee, then ebay would not be honouring their own promise and taking your money for nothing.
Typical ebay picking and choosing which conditions they abide by.
In any case, in most cases if ebay does not honour their terms, refunds can be obtained by contacting your payment provider, who will look into a situation a lot more thoroughly than ebay.