Forgive me for being blunt but you are asking for opinions so I will share mine. I understand you haven't inspected the rifle as yet, but even still, let me get this straight. You said you have no intention of paying 1200 for this rifle. Why not?
You are claiming to have a line on a minty, old Sako AV, that is an unfired safe queen and is chambered in a fantastic calibre. And to boot, it is/was owned by an elderly gentleman. Sounds like a real dream find and if it is in the condition described, why would you insult the owner and try to rip him off with what I call a "lowball" or "tirekicker" offer? Just pay the man!!!
I am not a Sako expert. However, I do own a similar older AV also in the 375 H&H. Mine is probably fired, but is almost 100% and has a gorgeous piece of gloss tiger stripped lumber from head to toe. This rifle is the fanciest gun I own and it is a safe queen. I don't even shoot it. The quality is unmistakable and if someone tried offering me 750 for it, he would be put on my ignore list, regardless of how high his second offer was.
I've never understood guys who play games. It's not enough that they find a perfect speciman and have first dibs on acquiring it. No, for some guys this isn't enough. They need to rip someone off to feel good about the deal.
I firmly believe in karma and what goes around comes around. You never know when the shoe will be on the other foot and wouldn't you appreciate someone not dicking you around and offering you a fair price? I know I would. In fact, I've paid more for something just because I really hit if off with the seller and want him to feel good about the deal too. And no, I'm not made of money but if I want something that bad, I pay for it!!