I have paid $8.50 for items. They arrive in a large envelope with 2 $1.00 stamps on it. How is this

[gutterpunkz05]

well for starters, out of the $8.50 you paid for postage, ebay takes takes close to $1.  Not sure what you call a large envelope, so we will guess  80c -  $1.50.  Now how did it get to the post office  IE  Time and Cost.  Dont know about your seller, but as an ebay seller I have a 60km round trip to the post office at 5km/Litre so approx $15.00 per trip.  So hope you can see that there is a lot more to take into account than the cost of the stamps.   Note  I dont charge for the fuel component but rather subsidize the post. And when I offer Free post I still have all the same costs.  When Australia Post under estimates post at time of listing and then charges 30 or 40 dollars more, I have never had a buyer look at the charges and out of the goodness of their heart offer to pay the difference.