Is this monthly or yearly because Ronaldinho makes 10 posts a year and ears 2 million Pounds and Khloe makes 2 posts a year?
A lot of sheep on instagram that will buy whatever these people post. Even people with like 30k followers can charge around $30-$50 per post.
Instagram theme pages are the only way to make money if you're not already famous or extremely beautiful with a perfect body. There are plenty of theme pages you can buy for $100 online that have real followers. If you try to buy followers, they will all vanish within 30 days. If you buy an account, make sure it has good interaction so it's attractive to advertisers. Making money on instagram is a business and you will end up spending several hours per day on it.