What? You don't just put shit in the dark and come back later, viola mushrooms?

:-p

Growing mushrooms is ... not really a pain, but a science lab.
It is not putting some seeds in the soil and seeing what comes up.
That could be deadly.

It is getting good soils, and then sterilizing it.
And then getting ONLY the spores you want into that soil, and keeping any other spores away from it.

People are indeed paying a lot for special mushrooms.
So, it can be a good business.