Don't take it, $250 is peanuts. You're providing a valuable service for them, and clearly they were aware of and encouraged it. I doubt they'd take you to court

Don't take it, $250 is peanuts. You're providing a valuable service for them, and clearly they were aware of and encouraged it. I doubt they'd take you to court, but I doubt they'd win anyways. There's no reason you can't own a domain with their trademark in it, as long as there's no confusion that you represent their company. Call their bluff, let them cut off your API access. They'll lose customers, you'll lose $250. Not even close. All that aside, I still wouldn't sell it to them just based on principle. You spent your time enhancing their product with their API, and they have the audacity to try and bully you into taking this ridiculous offer. FWIW, that's it for me ever using Zillow. I won't do business with a company with such low ethical standards.