I'm using it as a personal page and for emails. I don't need that money but getting a 200x ROI on a $10 investment made a year ago seems appealing. But, I fear to regret it in the future (10-20 years from now) where .com's will be very scarce.
So, how much do you think this domain's worth it? Have you already regretted selling one?
If it helps, ask yourself how much you'd be willing to pay to own your own domain name if it was taken by someone else. Not a perfect way to think about it but if the dollar amount is less than the amount being offered, maybe that helps you make the decision.
Can argue this applies for most sites too. If you visit the domain at least once in your life in the browser, you can forget about TLD as the browser will autocomplete it. And for finding sites, Google works.