> About a third of a cent per LED, not even counting the rest of the hardware!

At €20 per 32x8 module (2000/256), that's €0.078 per LED which is considerably more expensive than a third of a eurocent, I think? Even if it was €20 for all 6 panels, that's still over a eurocent per LED (2000/1536).

> I'm amazed at how cheap the LED matrix listed in the parts list is.

Cheaper now - AliExpress will sell you 6 32x8 boards for £59.21 (3.85p per LED or ¢5.16 if you're a colonial) saving you ~€52 over the original €120 price.