Crikey - refoams are maybe $20-30 for a single 2245 woofer like that ... (Rick Cobb, the ONLY source I'd use)
Does it include the grill over the woofer? No veneer chips on the lower edge?
I'd probably offer $550-600 next, and if he says no, ask him what kind of money he is interested in.
There are a lot of folks lusting over the B460 cabinets in very clean shape.
Its really nothing more than a big (18 inch) woofer in a rare but pretty box, with badges.
If he has a working BX-63A subwoofer included - well, they are going for $200 and up these days.
The other Q is: do you want it to keep, or to flip - the margin is different to flip ......