theoretically if you found a level 10 robe with
25 int
500 mana
5 crit
you could probably sell that for 5k+
level 10 stuff starts dropping at level 10 or so.
However getting 3 stats to line up is incredibly unlikely especially at max
For just a single stat a dagger with max ee at level 20 should sell for 3k+
In general anything past level 20 has an acceptable drop chance for good fg, level 55-65 is generally the optimal levels to find stuff as you can get drops worth 100k at that point, whilst the mobs are still reasonably easy to kill, level 65+ mobs just get harder and harder and generally better off reaching whatever level you need to MQ, complete the MQ and restart from level 1 and do it all again.
No magic luck is required, however it does help a little bit, how much it helps can't really be calculated. I'd recommend killing stuff faster rather than gettign magic luck as more stuff dead = more drops.