It's pretty much impossible to place a value on a collector kit. eBay can be really fickle.

As for the model, it was very competitive back in the day. Harry Latshaw, Dave Cotton, Ted Black, and Charlie Serie really made them go. However, the plane can't compete with today's sidewinder configured planes. The last of the Firedarts and other upright designs went to inboard tanks and offset engine mounts to gain a measure of G force fed fuel to make more thrust. You can see that on the Pardue / Langlois Super Burp (Model Aviation 12/78). I've seen them accelerate like a rocket and top out at 200+. It was pretty spectacular.

Also, the fuel tank as shown is too small to make a full run with the spec fuel mandated by the rules. It will also take a metal tank. The fuel will eat right through the resin coated wood tank.

The plane could be built with a U-Control system and flown 2-line as a fun model. If I were to do that it would be just as easy to copy all the wood parts and save the kit.

As far as your kit, send me a P/M and maybe we can do a deal if you're still interested in selling.