For physical weapons 15^50 is generally it. Daggers and one handed weapons (for casters) may be worthwhile with +5e and Scythes with 15^enchant (15^50 would probably still be more though). Good skinned one handed weapons with +x% damage/-1 health regen may be of some value too. +x unconditional are incredibly valuable as they haven't dropped since sometime in 2005.
For wands/foci, 20/20 would fetch the most cash.
I don't know too much about staves but they're a bit more flexible I think. For example, 40/20 is better than 20/20/something else if you're focused on one attribute.
For shields, bonuses with matching req's (eg, -2/enchant and +45/enchant, -2/stance and +45/stance, etc) can usually fetch a bit of cash. Old -2/-2 or -2/-3 shields (I don't think they drop any more) are very valuable. Shields with -5/20% may be valuable if you find someone that wants one. I don't think I've seen anyone interested in obtaining a hex set (-5/+60, as you mention); I don't know where you got that from.
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