Let me give you the perspective of somebody who did.

Been running 23 garrisons (minimum 10 treasure hunters each, rare missions and gold missions unlocked) since August 2015. Takes me 1.5-2 hours to do a cycle (empty cache and do missions on all 23), and mail stuff around as necessary. I would do that twice a week (often wednesday and sunday).

I could've easily done more. Log in and do missions more times per week, do the JC daily or professions, and I could've done better processes on auction house (I barely used it). But honestly it was boring enough as it was. Some weeks I only log in once.

It's hard to say exactly how much I've earned. Atleast 2.7 million, as I'm at 3.3m now, and 500k when I started. Since then I've given a lot of stuff away (around 25k crafting materials in monthly give-aways, because selling it on AH was boring) and I've bought some TGC stuff.

So I guess 2.7m divided by 208 hours is about 13000g per hour of doing garrison.

A lot of people tell me they do 10 characters in 30 minutes, and I should be able to do mine in an hour. I'm not sure I believe those people. I've been doing this for a long time now, 1.5 hours is stressful, 2 hours is realistic. Also, some people are underwhelmed by the 3 million, and think I should've made way more. I dunno, I'm sure I could have.