Couldn't find anyone for sale but I believe the last one sold for around 7.

I was with you on the green energy one but this one not so much. Ghosts and cauldron are sometimes above energy. I couldn't find any of these or ghost for sale since there are so few.

Honestly I could see this, green nrg, and ghosts going for more than all their currents given the trajectory of stahlhelm in general as of late and the rarity but without any links (or rather being able to find any myself) it's too hard to say, thats just a guess from my gut since I can't find any recent sales or any on sale so who knows?

Your suggestion for green energy and purples current price would keep them pretty close together, I'd say do 5-6 for this to keep purple just above green in the mean time.