Tarmack
Rhetorical Porcupine
Based on my findings (FYI, I'm a web analyst and I've been diving pretty deep into my analytics lately), and yes audience is a component, but so is the type of content/meta data we put up in the first place. I see very different ads on my main channel (Kleineganz) than I do on my second channel (EndressAnalytics). I'm the same person, with the same Google profile and they give me the same "recommended for you" videos - so then the only reason I would see different ads is because the content/meta data is different.
Also you want screenshots of my CPM? Fine here, you go. My channels (and earnings) may be small, but I'm pretty happy with my CPMs right now.
The advertiser only cares about the viewer. The channel content type is one of several ways that advertisers can target their viewers. The point being, that the network has little to no impact on the base CPM offered due to Adwords/Adsense operating all the time. Their purpose is to attempt to sell ad space at a higher value and add these advertisements to the inventory available for their partners.
Those high CPM values will not continue as your channel grows. The vast majority of ad impressions come from "Auction Display" which is also the lowest paying type of ad. When dealing with monetized views in the sub-1,000 range, the high spikes in CPM for specific ad campaigns (usually In-Stream) are averaged against a relatively small number of Auction Display ads. As the channel grows in size and views, those spikes impact the average less because the overall volume of "Auction Display" impressions is much higher, proportionally speaking.
If you joined a network and had your monetized views go up to say 20,000 over the next 3 months, your CPM would also go down most likely into the $6-$10 range most networks advertise. This would happen and you would blame the network for the CPM drop. You would be wrong however because it was due to the increase in the number of low value Auction Display ads your videos received, not a result of the network since the same Adwords ads are running all the time. And you would never notice the increased value of any ads the network did sell because that would be visibly lost in the shuffle, but they'd still be there.
Note, I'm not claiming a network will get you views. Most don't, barring unique circumstances. Just making a point.