I've noticed people have been selling their stuff for "good/reasonable offers" I dont thing that it should be the job of the buyer to make an offer, if its too low, they dont get it, if its too high, they get jipped out of their money, there will be the rare chance that they get the price you actually want for it.
If you are doing it auction style, list the A)Star/End time and date, and the opening price.
This is similar to people looking to buy items, dont say, write your price here, everything will be a lot smoother if you list the price you're willing to pay for it.
This is why we have a price check forum.