i am a frequent user of ebay, from overflowboxes, to marine books, calcium reactor and recently an aquac ev p/s.... and it's really damn cheap to get things their whether new or 2nd hand... its a big risk for buyers, trusting the seller, paying them upfront before shipping. Guess i am quite lucky w my previous deals, but most of them try to put a good reputation.... usual things i do before i bid;
1. ask questions to seller... u'd get a hint from their response if they r courteous enough and trustworthy.
2. check his feedback... most are regular ebayers... if quite new and less deals or with lots of negative feedbacks, i drop the item no matter how cheap and how nice or how urgent i need it...
3. check the actual retail price of the item outside ebay.... u cant blame them if u have to pay higher than retail price; u bidded. usually i give an allowance of US$30 for shipping so i know how much roughly i can go through the bidding process....
.... and in the part of the bidder, dont bid unless u cant pay...
hope this helps.....