Would it work, though? What sort of returns do you get on ads (meaning how many subs do you get out of them)?
I guess we're getting off-topic, but let me do some math for my situation. I started the campaign unknowingly around 35 subs or so. I think. I now have 155. So that's a gain of 120 subscribers, and the total cost of the campaign was closer to $250. So comparatively, if I spent $3,000 I would gain somewhere around 1,440 subscribers. Of course, my cost per view is probably high, and this is just guess work. Hmmm.
Well, two issues. Your campaign was poorly optimized. For those of us not in a huge rush, if you spend the time, you can likely get the view cost down to $0.01 per. Now, if you spent about $250 and got the 4046 views from your previous post, that puts your per view cost around $0.06. So, you got 120 subs. For the same spend, without any other changes than optimizing the campaign, you can estimate that at $0.01 per view, you would have gotten 720 subscribers. Then if you work on making your trailer even more engaging, that could otherwise increase the amount. Extrapolating that up to $3,000 would be 8600 susbcribers. Now, these are all guesstimate numbers but they pretty closely mirror what I'm doing on my end of things.
I know some large YouTube channels who have spent thousands of dollars on Adwords campaigns. The word is that it is not cost effective to promote a YouTube channel that only earns income from Adsense.
You need lots of subs and lots of views long term in order to recover those costs. The reason that Adwords/advertising works for somebody who is advertising goods or services is because when they get a customer, they can translate that to dollars. With YouTube subscribers, one customer is worth a certain amount of views. You know that we make PENNIES on views, not dollars.
From what I gather, Adwords has two main purposes for YouTube channels who are concerned with subscriber conversion rather than product sale conversion. The first is what I'm doing, where it's being used to jumpstart a channel. I don't get enough views through the organic search due to my videos being topical news. They get views for a short period and then nobody searches for that topic again. The theory is that if I can get up to 10,000 subscribers through adwords, by that point each video should be pulling around 1000 views within the first few days and the likes/shares etc will encourage continued growth beyond that point.
The second method is a burst campaign. This is done to boost a particular video up to 50K-100K views in a very short period of time, cementing it's position in the search rank. The video will then get solid organic views after.
For a channel like racegrooves, you're already gaining 5K subs a month and you probably wouldn't notice the increase of adwords until you were spending multiple thousands a month. But for me, where my normal monthly sub increase is around 10-20, getting 200+ in a month is excellent growth.