Personally, id pay them the lowest they were willing to accept
If they are willing to put in and more importantly, do the work for $500, pay em $500.
On the subject of KB, even though he appears to be good at what he does, i dont think we would ever hire him to work with us i guess we like to hire people who have a 'history' with companies that last longer than 3-6 months at a time [shrug].