Inscription has been a great market for me but it also takes more time than any other market I have worked with. I use ink of the sea usage as my metric of how much I am selling. I just know how much ink I use in a day so it is easy to track. On average it is 850 ink of the sea.
Lets do the math to see how much time inscription takes up. To get 850 ink, I have to mill 142 stacks of herbs. At 4 mills a stack at 3.8 sec a mill, that puts me at 35 min of milling. After I mill it, I then have to ink it. If each ink takes 2 sec to make, i'm at 29 minutes to ink 850 ink of the sea. I also have to ink the snowfalls for another 5 min. Lets just say its a hour of work a day to get the mats needed to craft what I need. 7 hours a week.
If I use 850 ink of the sea, I would have to guess that I make 500 glyphs. At 3 sec each that's 25 min of crafting. That feels very low from personal experience but I can work with that. At 25 min a day that's another 3 hours a week for crafting.
I have 1400 auctions listed at any one time. They either sell or expire and end up in my mailbox. I can only open 50 messages every 60 sec. So 1400 auctions is 28 pages of mailbox auctions. That is 29 minutes of mailbox time. I use the /reload trick to refill it quicker and I expect that cuts my time in half. So 15 min a night is 1 hour 45 min a week just opening mail.
I post auctions 5 times a day. If that only takes 10 minutes each time that's 50 min a day and 5.8 hours a week.
If I add all that up, I am sitting at 17.5 hours a week that I put into inscription. That is almost a part time job. I started small and just kept going and building and before I knew it I had a ton of time wrapped up into it. I would guess that I spend more time then that. These numbers were the optimal times based off the math of my ink of the sea usage.
With that said, some things I can start and walk away from. Like inking for example. Fill my bags with pigment and start the queue. When I return I have a bag full of ink.