If you consider your site(s) as a business, any simple business valuation would be accurate. Figure 2-2.5 times your yearly reveue. That gives a fair value.
Of course then you have to look at what you are selling. Just the site? The site plus open affiliate accounts? What are your SEO rankings? Are they improving? etc. etc.
I really don’t see how any of the automated valuation services could be the slightest bit correct.