I am interested in seeing what my site is worth with the idea that I might sell it and start afresh, its getting a little repetitive. How can you trust the 'free' assessments that seem to be merely stroking your ego to sell something?
You shouldn't ever have to pay to get a ball park valuation. A good website broker will give you an idea of what you could get for your site, based on your revenue/traffic #'s and the market right now.
If your website's making less than $300 a month, you're probably best just selling it at auction (with a reserve) and seeing what the market would value it at.
The problem from a sellers point of view is a site is only worth what a buyer is willing to pay. My suggestion would be to decide what its worth to you, and then accept offers. Only agree to sell when the price feels right to you.