When are non-perfect mods valuable?

My guess would be them being no longer obtainable.

Well there are 2 kinds of non-perfect mod that are going to be valuable :

* The pre-nerf mods that can't drop anymore. This include the sundering X/10% (note that the 10/10 can still drop), the furious <5% and the +25% damage against charrs. That's the one i'm remembering if i'm forgetting some feel free to correct me.

* Some mod with nice round number that drop on blue/purple weapons. They are not super valuable but you can maybe get some ecto from some collectors, this include 10% ench for staff, staff wrapping +1/10% or some other round number like +20 hp.

not entirely true, some mods are just very rare. if people need/want them they might pay relatively high prices. for example, im looking for 10% staff mods to make my sticks look pretty, but those only come on blue staves, and not very common. so i tried reeling them in by putting a bounty on them other cases what guy above me said is true, prenerf mods are always worth a bit, people like old stuff