You can charge extra per item if you wish, but buyers like it better if say 6 baby clothing items can fit into a 500gm satchel and you charge them only the $7.20, or have they gone up now to $7.85?

Rather than you charge them $7.20 for the first item and $2 for each item after that, then send them all together in a 500gm satchel, your then getting $17.20 for postage when sent in a 500gm satchel, i wouldnt be happy with that.

I always combine and reduce postage.

You can charge a fair amount for packaging but not for labour, and definately dont mention fees anywhere, your not allowed to charge for fees at all, but handling and packaging you can.