Well as a buyer from Australia (hence almost 
always an international buyer) I can understand 
both sides of the issue. One of the biggest 
problems I have seen is the difference in postage 
costs from country to country. 

Typically I have paid about $15 USD to have a cel 
sent to Australia (as its all airmail the source 
location rarely matters to the cost). This works 
out to be roughly $30 AUD. Now for $30 AUD I can 
probably send a typical house brick around the 
world, so there is obviously a discrepency in the 
shipping costs. By the way when I have sent cels 
it has typically cost about $5 AUD or $2.50 USD. 
So if the person is not used to the charges of 
your local post office they may well think you 
are fleacing them, at first I did, that was until 
I saw the actual postage cost on the package its 
self. 

So all I can say is what seems reasonable to you 
can often seem unreasonable to someone somewhere 
else (rediculous even). I suggest you simply 
check the cost to major countries, add a couple 
of dollars for packaging, round this to the 
nearest dollar and simply stick with this. 

However I should say the worst think I have even 
encountered is buying a cel (at a good price) and 
then finding the dealer is trying to recover some 
more money by uping the shipping costs (as I said 
it typically costs around $15 USD regardless of 
the country of origin), not that you are doing 
this though.

Hope this helps....