it's been so long since I've kept up with them. Pretty sure the Rappan Athuk, Abysthor single modules fell far in price. I don't think the M series/Maze of Zayene ones go for much either.  Maybe use NK's pricing, divide by 3 and see if it's worth it?

Noble Knight Games Role Playing Games - d20 Fantasy Adventures (Necromancer Games)

I think this may have been the old thread where they were being tracked (prices jumping up at the time)
D20 Collecting

I thought there was a list somewhere with the harder to find ones.
Complete guesses here:
FGG3 Ursined, Sealed, and Delivered
G4 Crystal Skull (I remember this being hard to find)
Lost City of Barakus
Vault of Larinn Karr
Hall of the Rainbow Mage (I thought this was hard to find, but according to NK it's going cheap)

edit: maybe divide by 2 instead of 3. Not sure on their prices at all. If you have a Crystal Skull I think it's got to be worth more than $17 (US).

Necromancer items have taken a hard hit in recent ebay prices.

Never Mind.
4 mint copies of R3.
7 mint copies of A1.
They used to be good sellers.
I could sell them all at £1 a book and it wouldn't be worth someone's money to ship it.
I think I'm gonna just offer an entire job lot up on Dragonsfoot, buyer collects.

I think the K-series, JG items, and Necropolis sell strongly.

Of course, then there's this money pit I posted about a few years ago

The former Non-TSR Recent Fun Finds Thread • Page 85 • Collecting General - Non TSR •  The Acaeum