Yeah it can be, but the problem I see is finding buyers that have enough capital and being able to grow accounts at such a rapid pace to make it worth while. Recently I've **heard** that @luxquotes was bought for 40k and another 1million follower account was bought for 20k. So there is money to be made but unless you are able to grow such accounts at a rapid pace I would personally stick to what I'm doing, I can make more money in the long run with the account.
But I have come across/watched this udemy course with a clever method:
https://www.udemy.com/learn-how-i-got-14-million-instagram-followers-in-48-hours/
Having a bot helps, and check my post #13 in this thread with the cheezburger reference..
Check post #55 in this thread, I recommended an ebook I read a while back.
Depends on your niche and engagement. But 30k can be good enough..!
Usually the correct amount of followers to demand a paid shoutout, but I know a person at the 20-30k following making over $100/day selling shoutouts, though he does work(contacts companies/people in his niche daily). So anything is possible. Take action and learn along the way.