I'm with Cyclegod on his suggestion.
Unless we are talking big ticket items the bidders are always shown (the big ticket stuff with concealed bidders is a croc of shit - just another ebay contrived scam). Contact all the bidders simply using a cut and paste of what you what to say which really doesn't take too long.
When Mr Seller doesn't get the high bids anymore for his shit that does the trick for me.
One for Nathan and others, and it's only advice, not criticism. Treat others as you like to be treated and remember that unless you are the owner of Kmart or some such enterprise then you are just one of millions of people world wide enjoying the buying and selling which evil bay offers we mere mortals. Some mortals are super efficient and honest while others are total slackers.
After years of buying and selling on ebay I have picked up all sorts of good stuff, often at very good prices. I have made some good friends on ebay and have been TOTALLY scammed by one individual who was just an out and out thief who with any luck has just been diagnosed with advanced penile cancer with the only cure being amputation !!! Thurlow Paul Schmieding of 28 Lee Circuit, Concord, North Carolina, you sir are a thief and a scumbag.
I never push either buyers or sellers as I realise people don't always put ebay first.
As to the postal issues, take charge of the situation. Let the seller know that you want the name of the carrier eg US Postal Service, the weight and dimensions of the parcel. With that info you can then access the relevant shipper and check their rates against what the seller has claimed and if you are convinced you are being fleeced inform the seller and provide relevant proof that he is overcharging and thereby resolve the issue BEFORE you pay.
Another tip is to ALWAYS insure the item and get a scan of the documents if possible or at the very least get the numbers of the 'policy' for additional proof.
On a positive if you have had a good deal the least you can do is use the feedback facility to let the world know that for your deal a least the person did the right thing - it's not hard stuff to do.
Thats my two bobs worth.
See you at the back of the pack in '08