It's only excess shipping if they charge you a significant amount more than they actually use (it's not just the postage you are paying for).

However, it isn't excessive shipping if they charge you the minimum amount required to cover them in a transaction dispute (like a trackable shipping rate). There may well be a cheaper postage option, but if the seller uses it, they would lose an ebay/paypal dispute if a buyer asks them to prove it was sent.

(apparently it happens - people buy stuff specifically to get the item free by filing a dispute, because the seller didn't use the more expensive shipping option with a tracking number)