Lots of valid points made here.
I think the thing that pisses off most customers is like a situation I had happen to me.
Bought a Kill-a-watt,sold for $15.99..
Shipping was 9.95 from California to NH..
When it arrived it was in a manila envelope( NOT a padded mailer) sent first class at a cost of postage of $.85.. Yea,eighty five cents and no tape used.
I can buy that manila envelope for app 25 cents.
That's $1.10 total and the time it took the guy to stick it in the envelope,maybe 30 seconds..
These are the things that make you feel like someone just lifted your wallet.