A few years ago I paid some sizable Game Of Thrones pages to promote my quiz and I was charged $50 or something similar(can't remember the exact figure), the pages too had a few 100ks of followers. I got a lot of visitors from page/feed post and story post to my site. For the feed post, they'd have to include my link in their bio.
To do this today, I won't recommend you pay per view. You arrange to pay a fixed amount, also negotiate it down if possible. But the most important thing is to see if the page is getting engagement. If the posts aren't getting comments and likes, then their story would be worse.
Depending on size and engagement of page, I would not recommend you pay over $100 per post. A lot of people now see IG and other social media as a source to make money so they charge exorbitant amounts even when the advertisers may never make profit.
