No buyer likes the seller who "loads up" by charging more for shipping *and handling* than is reasonable. EBay takes a dim view of that, too. Certainly, the buyer has a right to object when he or she thinks S&H charges are a ripoff, and if the seller doesn't specify in the item description either the S&H charges or the basis on which they will be computed then by all means e-mail him and ask...well before the auction closes.
If you're selling, why not offer buyers a choice of shipping: regular snail or Priority Mail? When I sell I usually specify Priority in my item description but I'll send something by First Class or Parcel Post if the buyer requests it. It's just a service I offer that keeps my customers coming back.