i think the seller has the responsibility to provide you the tracking code or else refund.

i would say buying online is at risk, no doubt. so think about the price, whether it is worth and make sure read the terms and condition before commit to join, because some issue is out of the seller control too, they are just human. if the item you can buy in store with cheaper price, of course it is better to get in store so that you can try and feel the quality.^^

i am a seller too, for the postage part i am sure other seller are not able to give exact postage charge ,there might be +- variance like purplecrystal00 said, they just want to make an estimation. if buyer would like to get refund for the postage i think the seller can make it they dont mean to cheat.. at least i dont 

and i ordered from ebay and lyn before, these seller actually did not use the postage method that i requested, pissed off when the item arrived like salty fish