No such thing as a "guaranteed appraisal" unless your going to back it up with a promise to buy at the appraised price should the person fail to sell the domain.
If you mean that you'll guarantee someone will give an opinion on the name, then to be honest, I'd far rather rely on a forum like this whereby you get a wide variety of opinions and sometimes the odd idea or suggestion that you haven't thought about thrown in.
Another reason your idea seems fundamentally flawed is that if you have 20 "experts" appraising a domain and your only getting $1, then they are only going to get 5 cents from each appraisal. I'd have to seriously question how much of an expert they were if they were selling their services that cheap.
Aside from all that, any value for this lies in the idea/service and not in the domain name itself.