The weight seems to be the biggest factor
Roughly speaking, for this size of box:
If it's 2 pounds or under, it's $33 or so.
Between 2 and 5 pounds, it's $50-something
Between 5 and __?__ pounds it's $85
This reminds me of international flights from JFK in New York. People flying back to their home countries with enormous suitcases, heavy as lead and filled beyond capacity. Which of course fail the x-ray scan, and then they had to be opened and checked...
![Facepalm2 :facepalm2:](./images/smilies/facepalm32.gif)