I wouldn't say that learning from a video is better than no training and I don't know anywhere that would charge the equivalent of $100 for private instruction. I wouldn't say that music is the same as martial arts where having an instructor is always good no matter how long you've trained, there is always more to learn, more to get right. Personal training is good but it needs to be good practice, taught by an instructor and regularly checked to make sure you are correct. Bad practice makes bad martial artists.
The video instruction may be very good but without an instructor to correct your stances, footwork etc how are you going to know if you are correct? How do you get to understand the nuances of which there are many in martial arts? However good the video instructor you are never going to have that moment where you can't make something work until the instructor moves one of limbs slightly, adjusts the way you are moving and voila it all becomes clear and the technique works beautifully, the video instructor can never do that for you, he can't look at you with the eyes of experience and say he knows what you are doing wrong and put it right for you. You will instead continue to do what you think the instructor is telling you to do and you will continue doing it wrong hence some instruction is not better than no instruction.
If you think we are going down the road of all or nothing it's probably because many of us are instructors who also have instructors and we know the value of face to face teaching as opposed to video stuff. It may be also that 'unteaching' someone who has bad habits from watching videos is time consuming and frustrating.
Certainly, at the higher levels of finesse, video instruction does break down a bit. There are definitely some problems students face where they need help from an instructor. I'd be a fool to say otherwise. A fresh set of experienced eyes will always be able to give fresh ideas. But I also maintain that as students progress, they develop awareness and don't need instructors to solve
everything. I've seen it lots, and I'm sure most instructors have, too. Students start saying things like, "Oh, shoot...I'm leaving my arms down too low." Or, "Oh, I am leaning too far right again." or any hundred little things that need tweaking. I catch myself a little bit 'off' all the time. Good instruction doesn't give a fish, it teaches how to fish (as that tacky old saying goes!). Teach students how to recognize things working or not, and troubleshooting. The more, the better. But they will still always be able to benefit from a teacher!
I have gained tremendous benefit from face-to-face instruction, have learned a lot being an instructor giving people one-on-one feedback and assistance...and I have also learned a lot from videos. That's why I'm happy to vouch for all of those angles and mediums, when they are good!
To give a more specific example of the video learning...every kind of gun work I encountered locally was garbage...I couldn't find anything good (up North, outside of hunting, we Canadians don't know much about guns!). I could tell right away it was all clearly being taught by people who have probably never fired a gun in their life (and had little concept of burning powder, kick-back, how to jam mechanisms, you name it). But when I encountered a small handful of actual military instruction videos from master instructors in different parts of the world...that was a revelation! Eye-opening, to say the least. Insights I'd never get locally. Raiding my dad's gun collection, working with a knowledgeable partner, firing guns at a range...all this taught me more than I'd ever have been able to learn otherwise!
Would it still be better for me to actually meet with some Elite Russian Special Forces instructor. Yeah. No doubt. But the chances of that happening are basically zero!
Now, I definitely agree, having to 'unlearn' people who've done things wrong is really annoying. Worse, those who insist that they are doing it right, or that they "prefer" it that way...and just do their own thing, no matter how weak mechanically or flawed strategically. But dealing with the intricacies of stubborn students and the pedagogical and psychological tactics involved is a whole other matter!