Woohoo, just robbed the Leyawijn vault clean.
Got a magic robe, a magic ring, about 500 gold, a pair of magic gauntlets and a set of armour. Also some diamonds/rubies etc. Oh, and about 50 books of around 50 gold in value each. Was extremely hard though, probably used around 1000 gold worth of supplies to survive the encounter with the three guards (fought one at a time, can't nearly handle three at the same time). But in the end, was worth it. After fencing should give me around ~3000. And I've got reason to go back there someday too, as there's an Argonian statue with text on it that my character can't read, and I need to find a book for it somewhere else.