You make some good points, the problem with 3D Printing houses, shotcrete and some of these other methods is that they cost less in the US where labor costs are

You make some good points, the problem with 3D Printing houses, shotcrete and some of these other methods is that they cost less in the US where labor costs are high and more in 3rd world countries where labor costs are lower (at least for the types of homes things like this are trying to disrupt). A really interesting alternative approach is earth bag building. It uses locally available dirt as a material and would generally work out to be even less than the brick building price you estimated. Here's a family putting up a 30' diameter building out of earthbags: https://www.youtube.com/watch?v=m5Xl8f2J3sY&t=130s https://www.youtube.com/watch?v=m5Xl8f2J3sY&t=130s It is _very_ labor intensive and as you said, it needs time to dry between courses.