This is not necessarily the case.
You could only use this new system if the old one fails, ie. only for the say 10% of users that block ads, and so even if it were more expensive it would still be more profitable than letting them block all ads.
But I don’t think even that is the case, as they can essentially just “swap out” the video they’re streaming (as they don’t really stream “one video” per video anyway), bringing additional running costs to nearly zero.
The only thing definitely more expensive and resource intensive is the development of said custom software
But I don’t think even that is the case, as they can essentially just “swap out” the video they’re streaming
You’re forgetting that the “targeted” component of their ads (while mostly bullshit) is an essential part of their business model. To do what you’re suggesting they’d have to create and store thousands of different copies of each video, to account for all the different possible combinations of ads they’d want to serve to different customers.