Frankly when I sell on Craigslist I build wiggle room into my asking price as people want to feel they 'won'. If I want 50 I list for 75 and if I get an offer for 45 I take it. Posting firm just makes them feel like they lost.
I put my old phone up at 200 a few months ago. Knew I wanted at least 125. Got 140. Everyone comes away happy.