Does that one have the ATI X1600 dedicated graphics? The graphics chip makes a huge difference to the price. I'd say R6500-R7000 max would be fair since that Macbook Pro must be around 3 years old now.
To give you an idea I have 2 Macbooks that I am selling. A Black 13.3 inch 2.4Ghz C2Duo, 250GB HDD, 3GB RAM for R6500 with OS X snow leopard and a 13.3" White C2Duo 2.1GHZ, 120GB HDD, 3GB RAM for R6000.
So judging from these specs I think R7000 is pushing it but depending on the graphics card.