I'm surprised no one has responded to this question so I'll give it a whirl.
If it was an original louver and good shape then $1,000 bucks ( US Dollars ) If he would take $600.00 then I think your doing good.
I could be low on that but when I see this stuff on ebay for $1,500 then it just depends how badly you want it and what your willing to pay for it.