What is fair priced for a 8 Year old TB?

I'm sorry but I don't have a picture. But anyways, my friend is selling her 8 year old gelding. I have ridden him multiple times and he is excellent!! She asked me to make a price and I honestly don't know. I am also an experienced rider and that is why she is letting me make an offer. I looked at other people who were looking at him and they would offer 5,000 for him. Is that too much? The TB doesn't have papers but is broken if you guys could help me out this would be great. :)