Can't upload assets via Open Cloud - confused!

Hi, I’m attempting to upload assets via Open Cloud. I’m just playing around at the moment but have run into an issue.

I’m trying to upload a video. I’ve got the API Key and I’ve run successful GET requests, and even uploaded images through the API just fine.
Problem is, when I try to upload a video, I’m getting this response:
{'code': 'INVALID_ARGUMENT', 'message': 'Actual price (2000 Robux) is larger than expected price (0 Robux).'}

Am I meant to include an expected price header or something? How can I let Roblox know that it’s okay to spend the 2,000 Robux?? :sweat_smile:
And yes, I do have sufficient funds.

Thanks for help in advance. Couldn’t find any documentation on this issue.