I believe if you do register it with the Library of Congress you can submit later drafts of the work without incurring the fee so long as the material and subject of the work hasn't changed significantly enough to make it classifiable as a separate work. (ie. you can make slight changes, revisions, corrections, but if you want to do something like add a completely new story element or plot-line that changes the outcome, or adds 30 minutes to the length, or some other such comparable change it becomes classifiable as a 'new work' and will require an additional fee.)