I have $30K of digital, HD video cameras. Mostly for on-location, multi-camera, live-switched video production. And I am thinking about setting up 2 or 3 cameras to do some more audio-electronics related YouTube videos.
But using a $5K (or more) camera to make YouTube videos is just silly. For that matter, using a $1K camera is silly. It reminds me of a quote from GearSlutz a couple months ago: "A $200 cable will sound better than a $2 cable. But not better than a $5 cable."
I will REPEAT what others have said many times here in this discussion. BECAUSE IT IS SO CRITICALLY IMPORTANT!!!! No apologies for shouting. For sufficiently-decent quality YouTube videos that viewers will find attractive and useful, it is quite possible that decent LIGHTING and SOUND are MORE IMPORTANT than the camera!
I intend to use $300 Panasonic cameras from Costco. I have already used them for some live online "podcasts", and with DECENT LIGHTING they produce pictures that are indistinguishable from my $5K cameras. The big difference is ability to handle changing field conditions, lens control, etc. etc. But for fixed "podcasting" video shooting like YouTube, you don't need any of those fancy features.
And don't get me started about "4K" Even local theaters with screens as wide as my house aren't running 4K. And 4K on YouTube is just a sick joke. Buy a camera that will put out a decent 720i video image and spend what you save on good lighting and sound.
Don't even consider buying a camera without a microphone input jack. And a proper headphone monitoring jack is a VERY close second requirement in my book.
But you don't need ENG/broadcast cameras with XLR and P48 to get decent audio, either. I have made quite decent corporate videos for a large multi-national high-tech company C-level executive with nothing more than a $5 "computer microphone" clipped onto his shirt pocket.
But unless you are quite close to the camera, using the typical "pinhole" microphone in a DSLR or the fake "shotgun" mic on a low-end camcorder, you will get a lot more "room tone" than is generally acceptable for semi-professional video. IMHO, Dave's videos are on the edge of what is acceptable for audio quality, but he affirms that it is GOOD ENOUGH for his audience (i.e. US) and perhaps I am more picky because I came from the world of audio before I got into video.
A $20 microphone IN THE RIGHT PLACE will outperform a $2000 microphone that is too far away. There are "headset" style microphones at prices around US$50 that are IDEAL for YouTube "podcasting" IMHO. You can generally plug them directly into the camcorder 3.5mm mic input jack, and use the camera's built-in automatic recording level feature. In most low-cost cameras you don't even have the option of manual control of audio record level. And for simple narrative dialog with a decent microphone placement, camera auto-level is OK.
A $300 camera WITH GOOD LIGHTING (sufficient lighting of the right kind and from the right directions) will produce video as good as anything you see on YouTube, and probably as good as much of what you see on the local even news on local broadcast television. And LED lighting solutions of a wide variety of sizes and shapes are so easily available these days at remarkably low prices, there is no good excuse for poor lighting.