I did a bit of testing in doom a while ago to see how fast the top tier donation item could theoretically be farmed. It of course relies on random drops from the bosses but here's what I finured.
The gauntlet takes me about 6 mins to clear and I have 2k luck or so. Arties drop reliably every three full clears. Sometimes more or less but an average overy 16 hours put me at 1 every 15 kills or 18 mins. 3.3 artys per hour. 10 in 3 hours.
So we are at 25 cents per 3 hours. 1.00 in 12 hours. So I was looking at 600 hours of doom grinding for the top tier donation item. 75 8 hour play sessions or 15 weeks of a full time Monday thru Friday job in the depths of doom. I'll admit a 25% standard deviation, but the best scenario is still at least 450 hrs if you can clear it in 6 mins or less.
Seeing as how awesome those items are, I dont at all mind the grind and love long term goals, but at the end of the day it would be a better use of life to just buy the item