As a seller, I  LOVE to get my items, delivered to my buyers within 3- 4 days of payment. That is one, priority that I have always had. I do charge my buyers shipping, but sometimes I quote them  the wrong amount  on an item. There has been plenty of times where I have PAID someone to take my item, due to mis-quotes on shipping. LOL ~That was my fault, as I always marked the priority shipping box.  So, now instead of saying that I ship priority, I always mark the parcel post box on shipping.  If I have ,extra money from the buyer for shipping, then I will automatically ship priority. If I have really over charged on an item, I refund part of the shipping amount through paypal. I try not, to ever charge, my customer a huge shipping amount. Nothing burns me more, than to receive an item that I paid  $8.00- $9.00 to ship, and find out that that it only cost $4.00 to ship.

A modest handling fee of  $1.00-$2.00 is not unreasonable to add to your shipping costs. This will help on the costs of your time for packaging, and gas to the post office.

~If you accidently  overcharge on shipping , kindly refund a partial amount.  Buyers will be glad to see that you aren't out to get them on shipping.~

You will become  TRUSTED seller AND they will BECOME a repeat BUYER.