Depends on the condition - 7/10 doesn't mean much to me, as maybe the cosmetic damage is in the back or somewhere else it can't be seen. Maybe 7/10 because it has a dented tweeter, but otherwise flawless. Maybe the seller is being very conservative, or maybe the speaker is worse than he's letting on.
Then there's age to factor in. A newer one in the same exact condition may get a few bucks more.
Then there's location. A local speaker may be worth paying a few bucks more for, as you'll save on shipping costs.
There's a lot of factors. Only you can determine what you think is a fair price. I bought a Bryston B60 a few years back for a bit more than the average used price. It had all the features I wanted, plenty of warranty, I was comfortable with the seller, and he picked up the PayPal and shipping fees. I paid a little more than the average, but I have zero regrets. I could have saved $100 or so by buying a different one, but it's not the one I wanted.
Keep an eye on market value, but don't let that be your only criteria if you plan on keeping the speakers for a long time. If you're looking to buy and sell within a short period of time, make sure you buy at a price that you can recover most of your investment.
If you're looking to get a price to list them at, I guess I just wasted my time :)
