I have a CX2, and know how much just the upgrades you have added can cost. I bet you can fly it outside with the extended shaft and tail boom (Flyrivesud - landing pad giveaway). That would be a plus with the Xtreme motors you seem to have and the batteries. Spare blades are always good for someone wanting to enter into the hobby as well as the crash resistant landing gear. A new CX3 is say $200. With some upgrades and extra battery, that might raise the price to over $300 right off the bat.

You didn't picture the charger, but I guess the eFlite charger is included as well as the manual.

Not knowing how many hours you have on the heli and estimating normal wear and tear. I'd say you might want to try between $149 and $199? With shipping?

I have to ask why so many batteries

Gilles