Fair enough, it'd be wrong for me to disparage hard working people but you can expect to get what you pay for, dealing with a client that requires significant education and guidance usually means higher fees or a very patient consultant.
I'm not talking about crowd funding. I'm talking about building it with the technical help from community members publicly. Like people are doing for lots of projects over on the open source hardware board https://www.eevblog.com/forum/oshw/
The fact you aren't openly sharing this here to get feedback tells me you're probably trying to keep it secret because you want to make money off this idea? That means you probably don't want to go the open source route which requires you openly share all the details of the project.
I suggest you do some research and learning on "hardware product development" to help educate yourself what will need to be done so you can keep an eye on what your consultant is doing/asking from you.
I totally agree on your first point, its pretty reasonable to expect that you get what you pay for but there are chances, maybe small, that I end up finding what I'm looking for, so I don't really want to give up without searching first.
About the crowd funding I guess I misunderstood you I'm sorry. As you mentioned before a microphone is considerably complex electromechanical device so I'm not entirely sure how long it would take me to get to a halfway decent result, it kind of seems impossible at least in less than a year - I could be wrong.
I'm not really secretive about the product, its just a decent slick looking desktop microphone with a nice knob and some lights on it, that's all.
I've already done some research, learned some basics about electronics, trying to find some microphone teardowns and take a peak so I can get a sense of what people already doing, searched for ICs and components and in general tried to make my self more familiar with many concepts. I'll definitely get more engaged and try to contribute by any means might make sense.
I just hope I stumble across someone that has already worked on such a project and maybe has a relatively easy time implementing it.