More towards that $400 than the $200 since they have the 3 axis gimbals- I see the helicopter and several different gopro mounts- plus your gopro- gopro remote, 3DR backpack, a small case for your gopro accessories- and assorted odds and ends-
Personally, I think I would bust up your package- list each Solo independently, and maybe list your gopro 3+ and accessories separately- It may take a little additional time and a couple trips to ship, but I think you will make out better.
I can see $400 for Solo with gimbal- and additional battery and MAS props-
Maybe $450 for Solo with gimbal, only 1 battery and 3 DR backpack and assorted 3DR pieces-
And either keep your gopro and accessories or ask $250 to $300 for all of your gopro stuff. I know the mounts are $20 and better each- so you have a bit tied up in gopro stuff plus the remote-
Your helicopter?? Not sure what you have tied up in it- but it’s something I’m sure someone would like flying around.
The best part- your Solos and accessories look like they were really well taken care of.