Not my opinion I've built far over 100 19" modules, 500 modules and mics... I think I must have used a ton weight of Audio parts, materials, cases.... Almost all major designs I have been built by now for myself. And yes, I've tried a few kit suppliers too. Like AML, Capi and M&M among others. And no, there is nothing wrong with the quality from them. No ripp off to customers. That my neutral opinion - not fair to say that about them....
It's hard to make better mics at this price point. Try it. In fact, their mics outperform most mics twice or more the price. Test their 47Fet Style or C12 Mics. Or the U67 Style with the moddified FB circuit, fantastic. By upgrading some components these mics are surprisingly good, definitely in the upper range then. Personally I think it's unfair to compare a Grosser or Telefunken as a reference with a price 15 times higher. By the way, I don't like all designs like Grosser's VF14 Fet Circuit. It will never sound like a 47 tube and costs an arm and leg. Any Archuts Dual 408A circuit sounds much closer to a good original Tube47 than this super expensive replacement circuit.
Honestly, it's more of a moral question how to commercialize designs and knowledge from other colleagues. The same goes for almost EVERY audio manufacturer out there who uses the circuit knowledge, the engineering knowledge,.... of Neumann, AKG, Neve, SSL, API, Fairchild.... commercially....and never paid any cent to them. You need names? You can write nearly every Audio Manufacture here under the thread...And that's another story. ...just my opinion about stealing - my 50 cents....