$70 Where did you get that from? Copyright cost $30 right now at the US copyright site. That's it. I just did one.One: your work is copyrighted as soon as you write it.
Two: editors ect. know this. Don't insult them by putting the little copyright symbol on your work or informing them you have copyrighted the work.
So do you need to copyright the work? Since you do own the copyright the answer is no---but--if someone were to take the work you have no proof it was yours other than your say so.
To dispel a myth here as well---many books have said that you can mail a copy to yourself and then don't open it--proof that it is yours written before the thief published it. THIS WILL NOT STAND IN COURT!
You can take a synopsis to a notary republic and get it notarized for whatever fee they charge. I have been told this will stand in court.
So, it is up to you. You have the copyright once it is written, but not legal protection if someone wants to steal it. Most writers are so much in love with their own work that they rarely want anyone else’s. As to needing it when submitting for publication---professionals wouldn’t stay in business if they were thieves looking for work to steal.
Shawn