Is overseas posting system so hard and timeconsuming for the seller?
Yes, that's why I gave up selling my uCurrent's internationally myself.
It's ok when you get a bulk of orders, like say 10-20 units, that way you can amortise your time of walking/driving to the post office, standing in line, processing, and doing the customer paperwork etc over many units.
But if you sell dribs and drabs, like say one unit this week, and it sells for like $50, it's hard to justify doing all that work just and the trip for that one unit that week.
If you value your time, then it might realistically take 30min to even an hour to do all that for just one unit. Even if you make $30 on that unit, you've just spent your time working for $30 to $60 an hour, just for the packing and postage, not factoring in the other work to produce it, so maybe half to $15-$30/hr.
Dave.