PR3 is pretty common -- I don't think a domain with PR3 alone is worth much.
The actual value of the domain would strongly depend on the domain name itself and the traffic that's coming to it, imo.
Agree with AlternativeWeb.
A pr3 domain can lose its rank on the next update too if the traffic is less or the backlink are getting removed.
Do not risk at buying just a domain if you don't know much.