Hello, everyone

Quick question - I was contacted by a start-up company about one of my domain names (
NutritionAPI.com). Right off the bat, they offered $800 for the domain name. They focus on nutritional values found in numerous brand-name products (Subway, Mars, etc). Instead of calling them with the number they provided, I decided to send them an e-mail stating that while I will consider selling the domain name, I am looking for a serious offer. Based on negotiation, what do you think would be a fair price? I know they need my domain name to boost their SEO since they are competing against a similar company.... Please feel free to offer feedback.
Huge Thanks,
Yev