How much are you willing to pay? Hit him with that number and tell him you can Paypal him immediately or send certified funds (or some other method of showing your earnestness.)
If the guy has other offers, great, let him take those other offers. But the "other offers" line is the oldest trick in the book. If the other offers were even close to $1000, he would have taken one of them already.
Just my .02
"The first lesson of economics is scarcity: there is never enough of anything to fully satisfy all those who want it. The first lesson of politics is to disregard the first lesson of economics." Thomas Sowell