So this is my personal experience: usually CR in a specific niche and with a keyword with clear intention is around 0.5-1%. So 200 people see the video, one or two buys. With clear intention keyword I mean that the video has to rank for a specific keyword that involves intention to buy or act (e.g. "how to build a website", "how to invest in real estate", etc.) If we are talking about a more generic niche (like if it's a generic vlog) and a generic keyword (like "I'm showing you how my grandma makes the best lasagne") then the conversion may be way lower, sometimes 0.1% or even 0.01%. It's all about how related the CTA and the affiliation is to what the content is about, and how interested your niche is in buying something.
But again, this is only my experience, don't take it as the big truth. I'll be glad to hear other people's experience as well.