I delete, many times, the items that I have placed into a cart, when the shipping charges are added onto the order, and almost double or exceed the total price of the items. I very rarely buy impulsively because of ridiculous shipping charges. I can't tell you how many times I bought small items, e.g. pipe-cleaners, packets of tobacco samples, which weigh very little, and they were delivered in an oversize cardboard box, loaded with tons of padding. The point is that the box + all the padding weighed more than what was shipped. I paid for a box that went into the trash. A bubble-padded envelope would've been sufficient, and cost me half the price of that useless box. Nor do I get any shipping choices, except regular handling, or the very expensive shorter-delivery time options.
Now, I rethink most of my online purchases, and only buy what I really need, or can't easily purchase.