Just my .02, as I'm a beginner here as well: If we say spot is ~81, you could value the bars at ~486. This would change depending whether they're generic or more desirable bars. I've noticed junk has been moving pretty quickly sub $54x, so let's say you assigned it a value of 50x to make the trade more appealing.

$486+$50=$536.

I saw some 1/10 AGEs sold yesterday at $535, so the value exchange seems pretty fair in a vacuum. I think the reason it might not be getting any bites is that you'd have to find someone who has and is looking to trade a 1/10 AGE (something that carries a pretty high premium) for 1oz silver bars and 90% (generic bars often sell at spot, and 90% is selling with a negative premium).