This all started when I realised that "KGT Factory Store" didn't have a listing for a 550mm linear rail (they had 450 and 650 though) and didn't want to bother them to add it. Instead, I looked around AliExpress and found "KGT manufactor Store" which had almost identical prices, but they were giving out a 5% discount for the order quantity I needed. This, as well as the existant 550mm listing, reduced a £204 order to £180. Then I saw that I was 2pcs away from a 10% discount, and so increased my 9H carriages from 4 to 6, saving £1 in the process. It could be possible to save another £3+ by going with 50mm shorter rail on some axes, having the carriage extend over the edge by 10mm, but I don't know if that would work so I don't want to risk it. I've got a better chance of reducing the length needed for the resin cartridges anyway; going from 600mm to 550mm would save £8.

I then decided that I was spending too much (£61) on the cartridge ballscrews and, after reading this forum thread on lead screws, I'm switching to belts and a 19:1 gear reduction Nema 17. I was also able to find 5pcs Nema17 motors for £24.09 (down from £28 from the same seller on ebay).

Back on AliExpress, I was going through my basket and noticed that the 7.6" screen was missing. Turns out the listing got adjusted and the screen is now only £35.20! That's even cheaper than the 6.6" 4K mono at £39.50. Now it's gone from a good deal to just plain BetterTM.