I can say from experience that an Instagrammer with 100k followers is unlikely to get anything near $2700 to post a photo. This was probably true several years ago, but these days the number is closer to $1000.
Now the ROI is worse, the advertisers start lowballing, and the content creators keep accepting (because rent is due and nobody else is offering any higher, sooooo)
As for the pricing of posts, the lowballing is getting more and more dramatic, because there are many more "influencers" now. The only brands really shelling out are large corporations with large budgets looking for something very specific. Smaller brands can just reach out to a bunch of influencers offering only product in exchange for a post, and someone will say yes.
I think we should all tread carefully here. In reality, monetizing content is not particularly easy and usually isn't ethical or sustainable.