For the price point the repeatability is uncanny. Of course this machine is still reasonably fresh so we'll see how it holds up over time but on 10 complete passes over a work piece that spans 80% or so of the total work surface the last cut is dead on on top of the first.

I'm actually quite surprised at this, I did not expect that to be the case. But: this is my first laser (previous CNC tooling: Lathe, Mill, plasmacutter, the latter a homebrew affair at 8x4') and the main advantage that it seems to have over the other tools that I worked with is that the gantry and the head are fairly light in comparison to what you would normally expect. Even a plasmacutter requires a movable Z in order to compensate for warp (or you will definitely have material strikes).

So the head is probably < 1 Kg all together and the gantry < 10. This most likely is the biggest factor in how with such a light and - bluntly - flimsy drive mechanism it works as well as it does. It's got less backpressure than a pen plotter would have, basically just the rolling resistance of the rollers and the drag from the airhose and a thin electrical cable. I did add a segmented chain for the main gantry to ensure the cables and hose can never get tangled.

As for the 400x, an industrial laser from a brand with a good rep runs between 20 and 40K, these open frame lasers sell from anywhere between 500 and a thousand $US, I mistakenly added a zero too much so you are right about that! I spent a whole day on writing that up and was super tired, I slept a bit since and it's much better now.