I have a possible opportunity to sell a small web application that started as a personal project and got a significant amount of press. The company that may buy it would benefit from owning the site because it brings many users to their site already. The site does not have advertising and does not generate a profit. It gets somewhere around 100k unique visitors a month. Though it doesn't have registered users, the site has about 77k unique emails entered by users.
I did not create this project as a startup or with a plan to sell it. It is only now that I am paying much attention to the stats.
In what range would you price this site? My first thought was $10k. I have no idea if that's too high or too low. I'm concerned that if I start too high, they'll balk.
I'd look at values on Flippa -- it's the most established and active marketplace for website sales. Particularly looking at the values of sites that have sold, you'll have a better idea of what a reasonable valuation range is.
Keep in mind that without having monetized at all, potential buyers will view your site as a much riskier investment than one that has at least proven it can generate revenue.
Congrats on your successful non-startup! Valuation of this kind of this kind of thing is difficult because it is very fact specific and every situation is different.
The fact that they approached you and are interested in buying your site suggests that it may be worth significantly more than $10k. The transaction costs (attorneys etc.) alone for this kind of purchase are probably around $10k.
Insist that the buying company make the first offer. That will at least give you a ball park amount. Then counter offer with something higher. Don't be afraid to name a high figure as they probably started with a really low figure. Then you can start negotiating. :) Feel free to have some fun with it as negotiation is what business is about and it is ok to drive a hard bargain. Just keep it friendly.
The primary rule of negotiating for a seller is to start high and then keep lowering your price until you can make a deal. You NEVER want to name a price, have them agree to it, and then raise your price. That makes negotiations turn ugly.