If i don't remember bad someone told me that 
there's an insertion fee, but what is sure is 
that if there is one it only applies the first 
time the item is listed, not for relisted items.

Also, if i'm not mistaken, i believe that there's 
an "auto-relist" feature for relisting auctions 
automaticaly if it doesn't sell. I have seen 
several cels stay on auction for more than 2-3 
years and when the auction ends it automatically 
goes back up for auction. It's impossible that 
the seller keeps doing this manually for so long 
time and also to be doing it as soon as the 
auction ends. One thing that supports my guess is 
that relisted auctions keep the same auction 
number.