It would be too stressful to find the right sized packaging when an item sells. I find it much easier to loosely pack things as when listing them and so when something sells then it just needs sealing and a label adding.
For me it would be more stressful to find the right sized packaging for every item I list knowing that many of the items probably won't sell. If I had to package up all 150 plus items that I have listed on eBay and store them, along with the other 200 or so items that aren't yet listed, they would take up an awful lot more space than they do at present, not to mention all the wasted packing materials that would be needed given that so little sells these days.
Still even if you don't pre-pack an item surely you know what the box and total weight it will end up being? And if you don't have a box that's the right size then wouldn't you rather cut it a bigger one down to size than pay a higher postage rate?
No I don't know what the exact final weight will be until an item is packed - all depends on the size of the box and what packing materials will be used. Using a larger box doesn't mean it will cost more to send if it's in the same band. I will have estimated the weight when I listed the item and that's good enough.
