I'm not a citizen of the USA. Why should I file for copyright protection in the US when international law and my national copyright already protects my images from violation?
The cost to register is minuscule. Having been in the business for 35 years, the ones who say the registering costs too much are the ones who by a Canon Rebel and claim to be "professional."
One can group register their unpublished photos, online, for $35. One can group register their "published" photos for $65. Build the costs into your business plan! Every other company has been raising their prices so why not us to cover the expense. Registration is easy and straight forward.
For those who do not know or think it is too time consuming, may one suggest learning how to use a computer. The total time to register a years worth of unpublished photos, including filling out the online application is about two hours. That is it. Yes, the legal route can be costly, but if you DO NOT stand up for your rights, you ARE hurting the true processionals out there.
If you are NOT a TRUE professional, then may one suggest leaving photography to the pros and quit pretending you are a "professional" photographer? Quit making excuses and LEARN how to be professional. Ignorance is no excess!
"Given that it takes too much money to enforce or bring a suit in a federal court,"
Find a lawyer that works on contingency. Problem solved. This will be impossible if you don't register in a timely fashion (i.e., prior to the infringement for unpublished work or within three months of first publication).
If you have the hammer of a timely registration (that hammer being the ability to obtain statutory damages and have the losing side pay your attorney fees) and the liability is clear-cut the other side has a very strong incentive to settle. Which makes finding that lawyer much easier.
I understand the need, have time, and know (or can gather up the information). Given that it takes too much money to enforce or bring a suit in a federal court, what is the point really, especially when I earn a living via non-photography job?