Hi,
I'm a knifemaker from Virginia. Producing a long blade with a hamon is very labor intensive. It takes time to apply to clay correctly, then you have to nail the heat treatment/quench and tempering. Somewhere in that process the blade surely warped, and straightening it is also a process frought with risk. But, once you have accomplished all that, you have many, many hours of polishing ahead of you. Geniune hamon blades are expensive for a reason. Good one's are hard to make, and take many, many, many hours. So, my point, I just can't conceive that the sword in question could have a real hamon, not at that cost. Just my two cents worth and my intent here is certainly not to offend anyone. Just thought I would chime in with a maker's view. I am glad you are happy with it.
From my understanding these blades are rolled, not forged.
There are other ways to produce a hamon without the need for blade, including dipping half of the blade in water and leaving the spin to cool by it self.
How exactly musashi is putting hamons on these swords is an unknown, likely automated.
The heat treatment on these blades is crap, they are far too soft and can take a set easily.
You are right though in that making a well done deferentially hardened sword takes time, but imagine if:
You had the blade rolled manufactured
You didnt take your time to apply the clay if you slabbed it on, hell you could nozzle out a hose to spray the blade.
Didn't matter if the heat treat worked or not, the point was to get a hamon (heat treat only to a soft metal skip quenching).
Polished by a buffing machine.
Since the blade is rolled nakago is pretty much the same so tsuka's can be mass manufactured to the same spec.
Overall they are well constructed in the sense that the tsuka performs like a tsuka, the habaki performs like a habaki. The blade however is too soft, the heat treat is crap. Overall I wouldn't recommend using them unless it's for water bottles, or milk jugs. And even there inspect the sword.