I've been selling on eBay for about 9 years, and want to let you know that not having a established account will hurt your selling price on a cell phone. The extent of which all depends on your listing.
So take the time to
double check your spelling, and have clear and well thought out photos of the actual phone with a
peice of paper with your eBay user name in the photo.
That will help alleviate peoples fears of getting ripped off. Also, while searching for what the Eris sells for, go to "advanced search" and select "completed listings".
That will show you what they actually sold for. You will get AT LEAST 200 for an Eris, even if you're a new user. But keep in mind, there will be fees that cut into your actual take.
So, you might be better off asking for $225 on CL. Just make sure you meet in a busy public place, during the day, and bring a friend with you if possible.