In many cases the discounted cost of the item combined with the shipping is reasonable compared to the full retail price plus the time and energy a shopper expends to go and get the item.
So if you buy a 32GB 3GS and break it a year later, the cost of a new one would be roughly $370, which is far better than the fullprice of $699, but still expensive.
It will charge extra-large flyers 75% of the cost of a 2nd seat on top of the fullprice for the first for "safety" reasons, a company spokeswoman said.