After doing product development work for about 30 of my 42 years in the lab, I found that there are very few things that can't be replicated, if someone is willing to invest the time effort and equipment to do the job properly.
Our purchasing department would send in a product that was "just like the one you're using" based on some manufacture's spec, or sales pitch. We would bring it into the lab and it would be a big fail. Purchasing was seeing big $$$ savings, but the product didn't cut it. Sometimes the company didn't have the resources to make the product, or didn't have the knowledge to break the competitors product down to reverse engineer it.
On the other hand, we had companies that would put the research in as to why something performed the way it did, often times, because of some particular equipment, and once they acquired that equipment, their product would come right in. We had companies in Korea who could clone German materials reliably. In a few cases, they actually improved things over the orginal by a large amount. We had a UK company that couldn't match a Japanese product, until they found out that a specific extruder was needed. Bingo! That was the trick. We had 3 plants in Georgia who mined and processed the same material, but one used a specific piece of equipment that made it process easily and completely. The other two plants wanted to use their equipment and they never duplicated that product, even though they would give it a similar product designation and offered it at a reduced price.
There's nothing really unique about a microphone circuit board. The parts are readily available, and boards are easy and cheap to build. Capsules are tougher, but dang, the Germans went to China and showed them how to build them. With current analytical techniques, you can pretty much duplicate the build. We're talking gold sputtered plastic film, brass, some screws, and some precision machining. If a guy in Virginia, or in Australia can make them in their shop, why can't a guy in Shanghai do the same.
What I can't understand is how they do things at the prices offered. I recently bought some plastic binding for a project. I ordered off Ebay, and it cost $8. It shipped from China, included some guitar picks and showed up in an envelope about a week later. How they can ship a microphone to the US from China for $14 with free shipping is beyond my understanding.