Look at "Completed Listings" for similar sales (there are bound to be several) and you can tell exactly what the going rate is.
List yours at a Fixed Price at the mid-high point and don't screw around with auctions. Sure thing, and usually much faster.
Used MacBooks are a commodity. If yours is particularly nice, say so and tell why.
"Money talks and bullsh!t walks."
As soon as you have received the money, send it on. Until then, ignore the static.