I've always wondered how online TV channels, either hosted on YouTube or on a website, guarantee return on investment, especially if the production budget is $20,000 and above
The most common method is advertisements. Advertisers pay the channel for the privilege of having their products promoted in a place where consumers will see it. (My source is me, btw - I used to work in ad tech until recently.)
This can be done in the form of in-stream ads that interrupt the main video for a few seconds (which is also what broadcast TV does during their "regularly scheduled programming."). Or it could be a banner that appears at the bottom of the video for a few seconds without interrupting the stream, and so on.
On a digital platform, these sorts of ads also carry the added bonus that they can collect information about you for retargeting purposes elsewhere. General location, content preferences (ie: you're watching THIS video so you may also like THAT video,) information about the device you're watching on, etc. This only affects the content creator's ROI in the sense that advertisers will pay more if they know they're getting retargeting data on top of promoting their products.
Finally, there's actual sponsorship money and product placement - at the end of the video when the content creator says "remember to like and follow and CHECK OUT THESE OTHER THINGS". It's of course possible that the creator really likes those things personally, but it's also very possible (even likely) that he was paid by the owners of those products to suggest his followers check them out. (Increasing the number of likes and followers also improves his marketability to advertisers, as it shows how big of an audience advertisers stand to reach.)
Product placement can also happen in the middle of a video, too. Have you ever been watching some kind of talk show and noticed that the host is drinking out of a mug with a particular logo on it? Have you also noticed how that logo is always conveniently facing towards the camera, even when camera angles change? This is not an accident.
All this is assuming you're not on a subscription service, of course. In that case, it shouldn't be a surprise where the ROI comes from (and they may use advertisements on top of your membership fees anyway.)