I recently found this out, this takes a bit of time to do but I think its worth it if done correctly you can earn more then 80,000 gold its recommended that you have a high sneak and pickpocketing skill with perks and a lot of paralysis potions it doesn't matter what bow or arrows you use because Calixto can't die til you get to that point of the quest to find and kill the butcher. You need to start the blood on the ice quest, if you have a high pickpocketing skill with perks you should have a 90% chance to steal the amulet off him but a 0% chance to steal the copies, after getting the strange amulet talk to Calixto Corrium to sell the amulet but before he takes the amulet off you go to your inventory and drop it at first he will pick it up and give it back to you he won't afterwards with the copies, after you drop the amulet he will give you 500 gold but won't take the amulet because its been dropped so you will only get the gold, what I noticed was that after this he has a copy of the strange amulet in his inventory and will each time you sell the amulet to him and drop it before he can take it if you do this a few times he will have 7-8 copies in his inventory its recommended that you wait til he has over 30 copies or even 50-80 copies of the strange amulet in his inventory you will get 500 gold for each one 30 x 500 will get you 15,000 gold depending on how many copies he has, pick up the amulet you dropped then when he goes to sleep break into his house and steal the copies off him. At this point you should use the paralysis potions on him once you steal them leave the house and hide he might become hostile you can then sell them back to him and get 15,000 gold or more depending on how many strange amulets you have and then repeat to get an infinite amount of gold. If want him to have copies of the amulet in his inventory only have 1 strange amulet in yours if you have 2 or more when you drop one he will take the other one and it would be annoying dropping 10 amulets and trying to find them all, when you go to pick up the amulet you dropped it will be listed as stolen so make sure you're not seen or you will get a 500 gold bounty and if you get caught stealing the amulet when you pay your bounty to the guard they will take the gold for the bounty and any stolen items which will be the amulet(s) and if you lose them then you are screwed unless Calixto has one or more amulets still in his inventory.
5 years later the one thing bad about this is that when you start leveling up from all the pickpockets you'll level up more and more encountering stronger enemies while literally only having the pickpocket at like max lvl. gl fighting arch mages at lvl 50 with pickpocket