I'm relatively new to selling items on e-bay but have been buying for a few years now. I recently had a clear out and sold a few items (to test the waters). I have to be honest and say I guestimated postage costs by using my kitchen scales and the post office website for weights and charges.
However, I would like to point out to some buyers (a few who have recently left feedback saying my charges weren't accurate), that other items are to be taken into account in postal charges, not just the amount on the postage lable. I put a flat rate on most of my items at £2 (which meant I actually lost money on the postage), the lable actual post office cost was £1.24 - £1.68 on most of the items and the bag they were sent in cost another £0.50 giving a total of £1.74 - £2.18. One of the items actually cost me £4.68 in postage plus the cost of the bag, bubble wrap etc, not to mention my time and fuel going to the post office.
I know that some sellers out there are boosting their profits by charging higher postage charges, but most of us just trying to "recycle" our items aren't out to make a huge profit from selling stuff on e-bay.
I hope that this will be helpful to buyers when making a decision on what score to give sellers on their postage - don't forget its not just the cost of the stamps that has to be taken into account.
Thanks for your time