If you don’t already know the enormous benefits of having your copyrighted work registered before infringement commences, then you should. This topic has been exhaustively covered elsewhere, so I will just start with the premise that it is always best to get your works registered timely. That said, I speak to artists' groups sometimes and the professional photographers always complain that they can’t get all their works registered because it would be cost prohibitive. Your typical professional photographer may take ten or twenty thousand pictures in a year.
When I mention the option of filing a Group registration, I am usually met with the objection that Group registrations are only good for 750 works. If you have to file separate registrations for each group of 750 photographs, that becomes cost prohibitive. That’s when I tell them that the 750-work limit is only if you use the official government form provided by the Copyright office. If you are willing to do just a little extra work for one Group registration, you can register as many images as you want with one form and one registration fee, currently $65. You took 20,000 pictures this year? Register them all with one form and $65. Do so, and all the enormous benefits of registration become available to you.