If you want to reduce the cost of the building envelope, possibly superadobe, shotcrete on airforms, ferrocrete, and flexible domes are better bets than 3-D printing of concrete. (The geodesic dome was conceived specifically as a solution to this problem, but I'm not convinced it actually does a good job at it.)
What's the current solution these things are competing with? Here in Argentina, the standard low-cost construction approach in the villas miserias is masonry with hollow bricks (18×33 cm), which cost 50¢. So a 6m×6m×3m building envelope requires about 1200 bricks, costing US$600 (AR$12000) if you buy them new instead of scavenging, plus some mortar and a corrugated-metal roof, which add a bit to the cost. It takes several days or even, at times, weeks to finish the construction; usually the family who live there build the house themselves, which is less of an opportunity cost than it sounds like with the unemployment rate as high as it is, especially among youth. Some families pour concrete slabs, others use dirt floors.
So, roughly speaking, this approach has to come down in cost by 10× to even compete with our current vernacular architecture, let alone improve on its pricing.
The concrete-3-D-printing approaches I've seen, like Andrey Rudenko's https://www.youtube.com/watch?v=DQ5Elbvvr1M, all share the drawback that they require a long time, because you have to wait for the lower layers of the construction to cure a bit before you can add more layers. Their big advantage is not that they're cheaper than pouring concrete into forms — although they may be, especially if you're building a large building or a dense construction — but that they have a lot of freedom of geometry.