I have several hobbies and sometimes I see something in a shop and think "that's a neat piece of kit, I'll have that", then when I get home I think, "well, yes it's a good piece of kit, but I don't really need it, so why did I buy it?".
If you're buying something on-line and you get to the check-out screen and find that the postage is more than the item you're buying, do you buy it anyway or cancel the order?