For example - a package that would cost me 8.70 to ship if I paid at the post office costs around 5.70 with Pirate Ship.
You do make an account and need to weigh your packages but it prints your labels and will also print a sheet for the post office to scan to confirm that you've mailed your packages (as long as you mail them the same day you print the label.)
This really saves time if you go in with multiple packages.