This a 50 min walkthrough of the design and manufacture of a 350,000 LED display (for a food counter in an airport) - it's interesting, I think, because it highlights various engineering challenges - size, weight, voltage drop, current limiting, static damage, decoupling of electronics from visual design, design of protocols, maintainability, and so on.
https://www.youtube.com/watch?v=9Qlmywxjau0via
hackaday - link to a photo gallery within.
(Each lit arc is about 2m long, containing two meter-long curved PCBs with very many LEDs, and many local driver chips hanging off a one-wire bus. The two PCBs are potted into a carbon fibre surround, I think.)
While we're talking about one-off commercial projects, could anyone share thoughts on how they'd come up with a price to produce a one-off project like this?