Yes. It is called discovery. The plaintiff will serve discovery requests (interrogatories, requests for production, etc.) seeking financial data regarding the allegedly infringing sales. You could seek a protective order to maintain the confidentiality of such information, but the plaintiff is entitled to discovery relevant to its claim. See Rule 26 of the Federal Rules of Civil Procedure. You would be better off retaining an attorney to discuss these matters in confidence, rather than make potentially damaging admissions on a public forum that can be used against you.
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Yes, it's typical in infringement cases for the plaintiff to ask the defendant to produce documents and answer questions regarding their infringing conduct (their sources, uses, etc.) and their profits and costs.
If the plaintiff is entitled to _statutory_ damages, then the plaintiff's burden of proof is easier and the only need to establish the fact of the infringement and the number of works infringed.
If the copyrights had not been registered, then the plaintiff would only be entitled to _actual_ damages plus defendant's profits, and there'd be a lot more discovery about the defendants' sales and revenue, and the defendant would need to prove their deductible costs.
If the plaintiff is also seeking an injunction from further acts of infringement, they also ask about the defendant's sources of the infringing works so they can also sue them.
If you're a plaintiff or defendant, hire a lawyer. Copyright infringement is literally a federal case and is definitely not a DIY job.
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The copyright owner would be seeking so-called indirect profits for the infringement. That means that even if you did not profit from selling the copyrighted images directly, any profit you made on products you did sell that could be tied to the infringing images would be recoverable.
You should definitely seek counsel quickly if you are in this position.