>>3461746>Worst that will likely happen is he gets something like a c&d letter from a lawyer.
The average american has less than $400 in savings. A good chunk of the population cannot afford the mere filing fees (paid to court) to file a claim themselves, let alone a single consultation with a lawyer to do it for them.
Every "threatening" mail you're safe to bin it straight away. A barking dog never bites.
The more formal and well articulated letters you might want to skim through, because in many places with common law, you're recommended/required to send a letter ("letter before action") before filing a case in small claims court.
The times I had to do it, it sent a calm, understated letter titled as above describing how I was wronged and what I was asking for and how I calculated that amount.
In most cases, they would try to explain things away (warranty claims, flights delays, etc.), or they would just ignore it.
But after filing the claim and them getting notified of it by court, most respond promptly.
Anyway, if you're serious about copyright, and within your country, that's what you should do. Not empty threats or invoice bullshit, just let them know what you're asking, why, being clear on explaining how you calculated it, and notifying them that you'd be happy to resolve by alternative means, or otherwise you;ll be filing a case.
Then file the case. Look up small claims court procedures in your country. You don't need a legal counsel. If you get it, you're not guaranteed to be compensated for it even of you win the case. It's a separate ruling, you might win the case but not have the legal counseling fees compensated.
Most importantly, if you have low income, at least in the UK, you can apply for a fee waiver, so you get a code and can file your claim for free. I've never paid to file a claim while studying there.