The material costs (the $300 per kg of titanium suggested in another comment) are only a small part of the overall expense. Electron beam sintering printer time typically costs $100-$200 per hour, and a large build can easily take multiple days.

After the printing itself, one will have to remove to loose powder, which for small cooling channels in the walls of the combustion chamber is very challenging and time consuming.

After that, some post-processing may also be necessary. One process for achieving the greatest strength is hot isostatic pressing, when the part is baked in a furnace in a retort filled with a very high pressure inert gas.

Specifically for rocket engines, it is also desirable to have a layer with the high heat conductivity on the inside, typically made of a copper-based alloy, and the external structure from a higher strength material. This means either bi-metallic printing, which is a rather niche process, or some metal deposition process over the printed part.

In addition to this, there is usually quality control, for example, high resolution industrial computed tomography, to make sure that the invisible internal features have been fabricated and cleaned out correctly.

In addition to the additive steps, it will also be necessary to machine the features which are impractical or impossible to build sufficiently accurately.

Together, these steps add to a significant cost.

Some of the above processes can be seen in this video: https://www.youtube.com/watch?v=7pXEf0wHU1Y

Mostly depends on the volume of the part, or equivalently it's weight. Complexity you get mostly "for free" when it comes to 3d printing. What type of material you need to "withstand temperatures and pressures of a rocket engine" is entirely dependent on which part of the rocket engine we're talking about. A fuel injector has radically different requirements than a supporting strut for example.

3d printed titanium goes for 300-400 USD/kg, steel is a bit cheaper at ~150 USD/kg for most inconel grades.

Paul Breed, from Unreasonable Rocket team - https://x.com/unrocket - mentioned, a decade or so ago, that he printed some aluminum engines for regenerative cooling by hydrogen peroxide for ~$1000 . Another story from http://rocketmoonlighting.blogspot.com/2010/ is about a small engine cooled with nitrous oxide - and manufactured entirely on personal money, also quite some time ago. I think these numbers are still indicative of the current prices.

Aluminum is magnitudes cheaper than Inconel. And since volume is cubic, and pricing mostly on based on powder weight, you are about an order of magnitude or two off for the size of engine ABL is producing here.

That's correct, but it's still interesting that you have that opportunity to shave - slash? - costs here.

And also the other engine mentioned isn't an aluminum one.

Would $100,000 still be a “steal” for all that? (Especially with repeatability and nimbleness) ?

Very. Very. Expensive.

Inconel powder is also Not That Great for your health and at the particle-size the printers rocket companies use, you need full PPE to safely handle the loose powder floating about.

The machines themselves are also expensive. Think in the millions of USD. EOS, SLM, and Velo3D are key players in this market. They require a fair bit of space, and training to use correctly.

You probably need a mechanical engineer who is well-versed in materials science and has a tolerance for finicky machines that constantly breakdown.

Then you have the metal powders. Which, also potential million or two.

And then you have all the associated infrastructure needed. High voltage power. Gas (Nitrogen, Helium, Argon, etc etc) in the thousands of liters per month. Waste disposal. Safety (some alloys are flammable in their powder form). Climate control (the powders are sensitive to the environment. Humidity will quickly destroy your powder supply). Tooling (the base-plates metal printers used are machined from solid blocks of steel).

And last but not least, any of the post-printing work. Heat treat. Coatings. Analysis. CNC Machining.

3D Printing metal on industrial scales is a CAPEX intensive endeavor, and not for the faint of heart.

Stratasys? I’m not sure about pricing, and the website won’t say.

However, a bunch of places rent out time on those machines. Draw up your rocket, and get a quote. Price is generally cc^2 volume

Metal is not cheap. Make a few out of plastic to verify dimensions.

Plastic to verify dimensions is a great approach.

But don't forget that the laser sintering of metal powders might result in design constraints not present in plastic printing!

side question to this: where can i design stuff involving metal parts (presumably in CAD tools) and have it printed en masse? With PCBs? ex) car components

You can draw up mechanical components in Autodesk Fusion, OnShape, SOLIDWORKS for Makers, or FreeCAD, and send STEP or STL to PCBWay or JLCPCB in China for manufacturing(note that export restrictions may apply if it's literal rockets or otherwise dual-use/controlled in nature).

PCB mounting outlines can be exported from above 3D CAD and imported to EDA tools such as Altium and KiCAD; KiCAD is fine unless you're doing DRAM or PCIe. Same PCBWay and JLCPCB takes your design, and optionally assemble PCB with parts for you.

That should take you to first 2-3 working units at ~$500 and up to few dozen beta units with zero initial cost and much inflated unit costs, and I guess beyond that involves significant human resourcing and networking problems outside of PoC hardware scope.

thank you so much for this detailed answer. now i just need to invest some time into learning CAD and KiCAD

You could try a battery powered phone charger since it's a "relatively simple" first project. The big hurdle for learning these types of tools is usually "What buttons do I press to create the output that I want.

For the electrical side, there are plenty of schematics online that you can try to copy or use as a starting point. And the CAD side can be a simple box with snap fits. I'd recommend OnShape if you're just starting out since it's the lowest barrier of entry, but Fusion 360 is also good. All in, it should be <$150 for the PCBs + Components + 3D Prints.

After you get the satisfaction of seeing your device charge from something you made, then you'll start getting the itch and find more excuses to make things.

I'll follow your recommendation and try the simple stuff. Looks like OnShape is right up my alley. All very exciting feels like I'm "programming hardware" !

And once you are done, services like Xometry allow you to print out the metal by having them source a printing vendor from their network.

3D printing is very popular right now. And for good reason. However, it often masks the fact that there are many ways to manufacture most products, and often, 3D printing is the most expensive one.

Meaning that instead of thinking "how do I 3D print this?" you should be thinking "how do I manufacture this?"

Something as simple as making a drawing, specifying the material and quantity needed and then going on reddit/r/manufacturing and asking "how would I build 50 of these" can provide very useful answers, even if you have to do a bit of research later to understand what you've been told.