Hello!
I find it hard to believe that they are making 9K a month out of advertising alone. Are they including sales and/or services in that amount as well?
I would recommend asking them for traffic reports (Google Analytics), to get a better idea of the site's traffic. You should also use Alexa, MajesticSeo, Semrush and others to further study the website's potential.
For the name alone, beeing a brandable, I wouldn't value it for more than mid to high $xx.
Best regards!