On my random survey, it will be x10 the earning your website able to make. For example, if you website is makeing USD1,00/ month from Adsense. You can sell your website at USD1,000.
This is just a general guideline. It still depend on how you promote your website, what's the traffic, your domain name uniqueness and also the relevant of your website content to the buyer. So, it is an open world. Name your price and if you can find your buyer. You are the winner. Cheers!