This is where I agree with, is you compare to the profit per minute the difference is not that big. I'm also glad that these pirates charge a big amount, I am also aware that doing so isn't really in role-play but neither is using a Barge as a trade ship. It's originally designed to act as a base of its own, operating independently, at least that's what I got from reading its description.
That of course does not change the fact that people still try, because its something new and challenging. Therefore, it's fun too. But yes if you ever get the crazy idea to use your Barge for trading you should have considered the risks beforehand.