What is the point of having any domain appraised, either for free or a paid appraisal?
If it's appraised for $100,000 and someone offers you $25,000 would you tell them, "Sorry you'll have to offer me 4 times that amount because some kid on a domain forum told me it's worth that much" ?
If it's appraised for $10,000 and someone offers you $20,000, will you tell them, "It's only been appraised for $10,000 so I really can't accept that much for it" ?
A domain name is only worth what someone is willing to pay you for it. It doesn't matter what your friends think it's worth, what your girlfriend thinks it's worth, or what some appraisal company thinks it's worth. Nobody is going to up their offer because you can show them a piece of paper saying "ABC Appraisals value this domain at $50,000".