I think you should charge per frame by taking your usual prices as a reference, and discounting the total to be attractive.
To get things clear, we will make assumptions giving the example above :

Let's call each frame a flat color sketch and assume a flat color sketch from the said artist is 30$.
There is 8 frames, it reaches a total of 240 $.
Each frame is the same pose, there is indeed a lot of work, but not so much interest for the buyer, so two choices :
- Apply a 20% discount to the total price which leads to 192$
- Apply a 30% discount to the total price which leads to 168$ AND charge for aditionnal effects if desired, like a second loop with a different expression for 40$ (which allow you to find someone that can develop a bit and cooperate with him for interactive turnaround commissions) that will lead you to a total of 208$

All numbers are just examples, I am not really the best at estimating prices and costs, but those formulas can help both the customer and you.

Thank you! It makes sense to meake the price work like that. My flats fullbody are actually a little cheaper so I have to make the math but yeah, this actually helped me out! I have to see what amount discount because there is not only the flat drawings but making the rotation work itself.

Thank you a lot for the answer man! Hope to be doing this kind of comms soon ♥

Ofc the discount doesn't match a lower amount of work, it's even more work that is involved here. But imo someone would rather buy 8 separate and different drawings than 8 POV of the same pose. Here we are not rationalizing the price in terms of work effort, but in terms of crude worth.
I'm glad I helped and hope you manage to find the good balance !