Why are extra characters still $3?

[Aenarion]

The point is that you can't log on multiple characters from the same account, which is why you need multiple accounts to trade with yourself.

Or can you?

depends, if you use the super dimensional bridge key item you can, but you'd have to first kill ifrit 10,000 times, then sacrifice 2,000 lalafells, find the legendary pony's magic dust, and mix it with a certain hamster's bone before you can activate it.