I only include the paypal fee if the buyer insist on the process going through with paypal.
I typically would accept cash or a bank certified check or a personal check for a purchase and would ship the item only when my bank tells me the check actually cleared.
I understand the buyer is slightly at risk in that transaction, but I prefer this as opposed to me shipping the item and the check failed to clear.
So, if they insist on using paypal, which to me is a pain to use, I tell the customer that they will be responsible for the paypal fees.
I could tack the paypal fee on the sale price initially, but that doesn't make sense to me, because once you list a price, that is the price. If the customer wants to pick the item up and pay cash (for example), why am I penalizing that person by tacking on the paypal fee?
anyway, my two cents worth.
Enjoy