You have joined a thread which is n early 4 months old,  and there have been changes /  improvements .

If buyers place items in their basket first,  then proceed to eBay checkout they will see a combine postage,  sellers find placing note explaining this on their listing , helps.

Also,  buyers and sellers get a message now,  when an item is purchased that they have a 3 hour window to buy other items and postage will be combined at checkout,  even if they have already paid for the first item.

This is new, so all members may not be seeing this, hopefully it will be rolled out to everyone soon!

@livehappy2015