Hopefully others here can offer a much better answer than I can, or at least correct and improve my reply. Usually when forum questions are met with mostly crickets, it is because no one has a great answer ... and that is me right now. Also, I'm always the guy that pays too much for things, and then can't find a buyer when it's time to sell ... so don't read too much into my reply here, because I don't know much of anything.
I can tell that this was a really nice collection of gear for it's time. Two hexacopters, nice goggles, 4 gopros, spectrum dx9, quality battery charger, good collection of batteries ... all pretty much top end stuff and it looks like they were well taken care of. It wouldn't surprise me if this represents a few thousand $$$ worth of original investment. Many of those items would have been a few 3 or 4 hundred $ each individually at the time of purchase. But it also is from a few years ago when you had to put in a fair amount of DIY effort to build your systems from various major components to get high quality results. Today most people would just buy a mavic or phantom which do pretty much everything right out of the box in a simple integrated system.
Selling stuff for a fair price is always hard -- even more when it's not in the mainstream of the technology hype curve anymore. You might find people that would be interested in one or two aspects of the collection, but wouldn't be able to pay a fair price for the whole thing. You are kind of limited to your local area, unless you want to start parting the collection out, boxing things up, shipping bits all over the country or maybe the world ... that ends up being a lot of effort for the few parts you would sell, and probably not really worth your time. But still, this collection represents a lot of care and thought so it would be a shame if it doesn't find a good home somewhere. You are probably looking for someone who would appreciate the DIY aspects of this collection.
If you haven't tried craigslist already, you might try there. And I know facebook has local sale groups for various areas. Ebay will give you a much wider audience, but you need to be willing to part things out and ship all over the world and deal with people all over the spectrum. If there is a local hobby shop or model airplane club, you might try contacting them to see if they can put the word out.
Personally, the two hexacopters caught my eye, but I don't fly spectrum so the transmitter wouldn't be much use to me, I don't really do gopro's or fpv so that aspect would be less interesting to me. Some of the batteries I could put to good use. I suspect most people here will have different, but similar sounding stories ... (some parts interesting, other parts not as much.) I live many states away from FL (I am in MN) so I can't just stop in and make a cash offer.
So if I personally was going to come up with a value that I would be willing to pay, here is what I would be thinking. If I bought all that stuff for a few hundred $, (let's say in the $300-400 range) I would feel like it's Christmas morning. If the negotiations started climbing close to (or well past) $500 because that would be a fairer value ... then for myself personally, I would start thinking seriously about need vs. want vs. my family budget and probably have to walk away because I just couldn't justify spending that much right now on things I can survive without.
I echo all the other sentiments here and well wishes for a successful sale. It is clearly a quality collection that is well taken care of. It represents a sizable investment. A "fair" value is probably well over $1k, maybe a lot more? But I have no idea how to find a person that would need exactly this collection of equipment and be willing to pay the full fair price?
That probably doesn't help much, but those are my thoughts if I try to put myself in the place of a perspective buyer.
Best regards,
Curt.