I sold something big on eBay. I used UPS's website to calculate shipping charges to make sure I was charging enough shipping.
I went to the store and they told me it was $20 more. After it was all over, I ended up paying $78 for something that I received $75 for (including shipping costs). I would have been better off putting it out for the trash! The problem was that it was a big package, so the actual weight (on which the website estimate is based) is irrelevant.
They added close to 30 lbs. to the shipping weight.
Monetary Loss: $20.