Okay here is my math.
1 Rabbie Basic pass ran solo nets me approximately 10 skeleton fomor scrolls, 20 red skeleton fomor scrolls, 10 metal skeleton fomor scrolls, and 30-40k in just plain gold.
10 skeleton formors = 7,800 gold
10 red skeleton fomors = 11,100 gold
10 metal skeleton fomors = 15,900 gold
The quest scrolls cost 30 gold to purchase, but that's trivial.
So one rabbie dungeon run can pull:
+ 7,800 from skeleton fomor scrolls
+22,200 from red skeleton fomor scrolls
+15,900 from metal skeleton fomor scrolls
+30,000 from direct gold drops
=75,900 gold for a typical run through Rabbie Basic.
Now you might get less from a poor run, and I've gotten as much as 100,000 from a good run. But that is one of the richest dungeons in the game to loot whenever someone needs money. Unfortunately, a newbie is going to have a hard time even finding the pass. So if you can't at least do Rabbie Normal to slay the Black Succubus, don't count on it.
However, you did ask how the people with a lot of money got it.