Ask HN: How do you value a website that is on the first page of Google?

I run a website that is ranked on the first page on Google for quite a valuable keyword. When you search for this particular keyword, Google shows over 450 million results.

The website has about 5000+ unique visitors a month.

The actual website does not generate any money as I'm not selling any products/services or advertising.

I've now been approached by a company that is interested in buying the website due to its placing on Google.

How would you value such a website? I assume it is more a question of how much value the potential acquirer perceives rather than hard numbers.

Please share your thoughts.