Hmmm - dont know an answer - why should I give them away? They are cheap, so money would not be a reason to sell them.
The different mods show slightly different flight characteristics, tinkering and trying different mods is also quite fun - you can try and fly the helis in your living room, dont have to go out to a hall or field for this.
Anyway, actually I am not doing a lot with my Solo Pros (and Bravo SXs - similar, better flying Nine Eagles helis with even better flight behaviour), Blade mCP x is more challenging in flying, Walkera helis are more challenging in repairing (and flying).
But those Nine Eagles helis are easy to fly, easy to repair, cheap, ... nice. Several scale canopies are waiting to be painted and fitted to the NE helis... when I find time... they are simply fun, I like them.
Collecting tiny helicopters - dont you know this addiction?