I have a client who ordered art from me that they asked be private between us, due to it's embarrassing nature. The extent of the agreement was "Don't post this online" to which I said "Okay."
My commission rate is less than 50 dollars. After completing their work, I discovered that this client is a very wealthy and divisive politician. This presents challenges and risks to myself that, had I known prior, would've changed my price to reflect the burden.
I have contacted them and made clear that I must increase my price to 150,000 USD, or I will have to refund them because I cannot reasonably secure the art against a sophisticated attack that a political opponent can mount, and may just release it to the public to eliminate their interest in me, for my own safety.
They have threatened to sue me for defamation and black-mail.
Do they have a legitimate case against me if I release the art and give them a full refund? I won't interpret any answers as legal advice, I am only doing preliminary research while I save money to consult an attorney.
Addendum: It's worth noting that the "NDA" in question was very weak and never specified a duration, penalties, scope, and was never in formal writing, merely as a casual email exchange.