I had a ton of rare Dunwich that I sold right before the retirement. I was pissed for a second or two but then moved on. I don't think the incredibly high prices will last much longer. The new cats won't care about this stuff in a year or two and I think the dirty little secret is none of the Dunwich stuff was ever really (imo) that amazing. It's a hyped brand and I think a lot of that hype wasn't justified.
I find the Dunwich stuff to be pretty amazing, particularly if you are into lower register playing (bass/tuned down guitars).
The scalper prices suck but you see it across the board. Anything that is hard to get that has interest went through the roof. Dunwich isn't alone. Look at moog, 3leaf, Iron Ether, Dwarfcraft, CooperFX...
I wouldn't get annoyed that you sold stuff that became worth more...I think we all have done that, particularly if you've been playing instruments for a bunch of years. I just have a hard time believing things are actually trading hands at these ridiculous prices, but I know it happens. Blows my mind.