what you need to understand here is the cost involved to to serve the video add not just the platform- its quite expensive (from the agency/client end) ie. cpm cost (cost per thousand unit)
so you would be best to compare ad serving costs across all mediums - Facebook Instagram online tvcs etc
also I would look into programmatic trading as its a huge way video is being served now
haven't been in this game for many years but its rather complex
