Shining Gyarados JPN

What’s the practical value of one of these? Someone wants to trade me one, and I’d only do it if I could re-sell it immediately for a good amount.

I looked on eBay and they seem pretty expensive, but they also don’t appear to be selling.

Thanks for your help!

which shining gyarados your talkin about the one from HG/SS or the one from neo revelation?