This is an accepted solution.
It can vary quite a bit based on your niche, geography and what you need from them. Best to just reach out and ask a few for there rates to compare and negotiate. For a rough ballpark, check out this tool. They also have one that checks for fake followers that is useful. Links below.
I actually just created a blog post for this! https://blog.getcarro.com/influencers/paying-influencers-what-brands-need-to-know-in-2019/
The general consensus from a few sources is between $210-720. That's quite a range, so you should set very clear expectations about what is required before agreeing to pay the influencer. Can they recommend other products in the same 24-hour period? Do you have any rights to share the image after the promotion is over? Will the influencer send a hi-res image of the promoted story so that you can use it on your product pages and your social ads?
The linkr platform calculates a media value for each piece of content created by individual influencers, based on factors such as content quality, content type, reach, exclusivity, value of provided product samples, etc. to ensure maximum outcome for any given budget.
There's a free plan available, so you can already check out what an influencer with 50k - 70k followers would charge: https://apps.shopify.com/linkr