Would it be possible to use 3D printed node based structures to make cheaper GA planes?
3D printing is unlikely to make anything cheaper in the near future. With current printing technologies it's an order or magnitude or two more expensive per unit than volume manufacturing techniques such as extrusion or injection moulding.

It's notable that the company you link to chose to make a supercar rather than a low-cost small car. There's little price competition in that market, as brand loyalty dominates. Most supercars are bought as status symbols or for fun rather than for their actual road performance. Most of the incumbents manufacture very small runs with a lot of hand assembly: exactly the kind of manufacturing that 3D printing is competitive for. On top of that, because of the status symbol marketing, there's huge room for new players to differentiate based on a green image. Tesla has done this in the last few years, which is why some of DMF's marketing material focuses on dissing electric cars.

Runs are small in GA too, so there's potentially a wider niche for these techniques to fit into. The market that would most closely fit IMO is kit aircraft. A kit that's primarily 3D printed parts joined by standard spars, with a flexible outer shell, could have shorter lead times and less tooling cost.



After discussing this with some mechanical engineer colleagues today, they pointed out how 3D printing of metals is now being used as a complement to CNC machining in the rocket industry. For a part that has to be machined from a single piece of metal, they 3D print a shell that's slightly larger than the required shape, and then machine it to the correct shape. It allows you to achieve the tolerances you get from machining (which 3D printing can't yet deliver), but without the waste you get from cutting down a solid block.

It's an aside to the main question, but it's a way that 3D printing could be used to reduce the cost of some components and allow designs that would have been economically infeasible.