I write to sellers all the time.
Many just don't know there are cheaper alternatives.
Some others are trying to generate a lot of extra money and think you are too dumb to notice.
There are a few who are trying to make it as commission selling companies. (We list for you, etc.)
These people are often asked to sell an inexpensive item on commission. 15% of a $10 dollar item ain't much.
So all of these people put big fat shipping charges on.
One thing, Ebay now makes insurance totally the sellers responsibility. If you don't insure and something happens, you have to pay all the money back.
So insurance is customarily added to shipping by sellers on everything now.
USPS flat rate is clearly the best deal in shipping small packages right now. Weight doesn't matter, its the cubic footage.
For larger heavier things though, they are terrible. Awful criminal expensive.
Fedex ground is the current leader on larger packages. Far and away.
UPS doesn't really want your business. They want the big accounts.
If you bring a single item in, they will crucify you. $8 minimum on top of the regular shipping, and $10 extra if they have to come to your house to pick it up.
But if you have a big commercial account and ship dozens or hundreds of packages, they are terrifically cheap. This is why Amazon and every other largest shipper uses them exclusively.
yours Scott