Sell it!!
It's a plastic model aeroplane kit. No more than that.
The kind of money they sell for makes it madness not to sell. With the money you get, you can buy plenty of models to replace it, enhancing your enjoyment.
Plus, every time you look at it after you built it, you'll think "$600 - not sure I got $600 of enjoyment out of that"
In addition, I personally believe 100% - thanks to good old capitalism - that we will see the Gotha kitted again. Not by WNW, but by whomever buys the moulds & IP.
The things sell for ridiculous amounts. It has somehow obtained mythical status. A short-run, priced competitively, would sell well.
It won't happen for a good while, but it really is inevitable, especially as technology reduces moulding costs. After all, the moulds are just sat there, doing nothing - that benefits nobody whatsoever.