Is There Not A Huge Difference In Earnings If....

I've looked a bit into legit youtube makers reported earnings, as well as the various earning estimators, and what I've noticed is the average earnings is $0.75-$1.5 CPM (after all the fees and such).

These numbers seem to apply regardless of niche. But how can it be possible that a prank channel targeting untargeted 12-25 year olds earns about $1000 per 1 million views, while a medical/fitness/health channel with a much more targeted and buyer-friendly audience earns about the same: $1000 per 1 million views.

If it was webpage-based adsense, medical websites would probably have a 5-30x higher CPM than a website about pranks in da hood.

Is youtube somehow different, or is all the information I've been hearing just somehow way off?

Since YouTube CPM is much lower than AdSense CPM, the difference between the different niches is smaller. In percentage terms, you will find similar differences though.

The interesting thing is that "entertainment" content like funny videos has a much more stable CPM on YouTube than on AdSense...

As tobisar said, the difference on YouTube is much smaller. It's kind of random. Obviously prank channels are going to pay low-tier, but maybe you'll earn double that on a more technical channel.

If you're going the adsense route, I can only suggest you focus on viral traffic since the difference is less pronounced, but the niche is far more wide-stretching. It's better to generate 1 million views in the prank channel and earn $0.75/cpm than it is to spend that same amount of time generating 200k viewers in the medical niche and earning $2/cpm. The former will earn you $750, the latter will earn you $400. You'll generate far more traffic in the prank niche because there are WAY more viewers for it, and it's viral potential is enormous. Technical niches have a much smaller audience. For adsense, the right play is to go big and go viral.

Hopefully though you can see the futility in it. It's very little payoff. It is basically worthless.

My advice would be to pick a technical niche and use it to promote affiliate offers. That way, instead of earning $2/cpm you can earn $100/cpm.

As to why this is, it is because YouTube ad traffic converts far worse than normal adsense ads. Thus advertisers haven't picked up on YouTube ads that much yet, and most of their advertising goes unpurchased, thus the CPM prices are very low.