Think about how much you paid for it, renewals, etc. as well as how much time you put into advertising it for sale elsewhere (or even developing it into a website). Factor in how much you believe your time is worth with the addition to how much you actually spent out of pocket.
Then, take that offer and see if it's a decent return on investment from the figure you came up with.
If you're satisfied with the price, take it. If not, counter offer and see if they bite or meet in-between. In the instance you can't come to a mutual agreement, don't sell and hope someone else will buy it for what you want. If you take this route, you're adding another year of renewal with the unknown that it may not sell within that 1 year, etc.
This should be considered for all names in addition to many other metrics not discussed.