You do have to be careful, its a case of knowing what you want and what the value is before starting to bid.
I got a decent set of David Clark H10-60's just over a year ago at about £115. Which were as new, and less than half what I would have paid at popular pilot shops.
On the computer kit front, I was recently watching some bluetooth GPS receivers sell for more than you can buy them new.
You also have to be careful of getting stung for import duty when goods are sent from overseas, I have had a couple of friends caught out by this when buying computers that are shipped directly from "our warehouse in singapore".
Jeth