For one, this person seems to have some very advanced knowledge of some very advanced processes - I am not even sure where one would gain such knowledge from easily, though they do seem to have access to MIT in some manner. Regardless of how it was gained, this knowledge of some of the very basic processes and advanced tools involved would be foundational to this entire enterprise (and it seems this person went to the trouble to build up to this - but what foundation of knowledge they had prior to that point seem unknown?).
Secondly, they appear to have something more than just a simple "2-car garage" - unless the camera perspective is really skewed. The building they are in looks to be like a large steel fabricated unit, 40'x 20'x 12' - my numbers might be off but it doesn't look like a simple garage or workshop, but rather something you'd either pay a lot of money for to have erected on your (likely sizeable) property, or its space at a leased business/industrial complex.
Third, from what I gather, much of their equipment is resold industrial surplus off ebay (and probably other places); I know of one company, local to me (Phoenix), which sells online via ebay such equipment (Equipment Exchange) - assuming they are still in business. While what they sold was inexpensive - even at "pennies on the dollar" you are not talking small amounts of money, because some of that equipment is anything but inexpensive brand-new. I'm sure there are other vendors as well for this kind of equipment, and if you know what you want and need, you can probably strike some good bargains, but I still can't imagine this being budget friendly for most people.
This all adds up to what seems to be a "hobby" that would require both extreme dedication (time, energy, and knowledge acquisition) and considerable monetary resources to implement. Not something that just anyone can do - it's not a "maker friendly" endeavour. Maybe it can be miniaturized and simplified now that it's been "proven" to be possible, which is a great thing in itself (after all, it was more or less done with 3D printing and home CNC). Though I am not sure how far that can be taken - then again, people have fabricated some quite complex stuff before...
So all in all - this is amazing work, and does show the possibility. But temper that with the reality of the situation: This person has some very specialized knowledge gathered over who knows what kind of timeframe, and the resources to purchase and bring together all of these tools and parts to do this kind of thing. Even with all that, they still had and have a bunch of trial and error. I'm amazed it could be done at all in a nominally "DIY" manner. Congratulations to that!