I agree that $6 shipping is excessive.  One potential reason for charging some shipping would be to actually incorporate a physical object into the auction and ship it to a verified address for the recipient.  That would, I believe, per ebay/paypal policy make the auction subject to seller protection from chargebacks.  For example, if I sell 1 trinket on ebay, with a "free" gift of 10BTC.  Then I can ship the trinket via certified mail or something else with tracking.  The sale is no longer in violation of the TOS, and in fact is subject to protection from fraud the same as buying or selling anything else on ebay.

*The above is based on my interpretation and experience doing limited business on ebay with paypal.  Obviously read their docs yourself and come to your own conclusions if you are going to try it.

In the spirit of this thread, I'll mention another trick I've seen used.  Ive had buyers "buy" BTC from me, and then wait ~24 hours to pay or cancel the transaction.  I assume they are watching the price and then only complete the transaction if the price shift is beneficial.  This was in the bitcoinmarket.com PPUSD exchange.  It obviously doesn't work in markets where both currencies are already on deposit with the exchange.