Remember that every X1000 is different, assembled bespoke to the customer's order with care. This is not a low cost budget PC that is quickly thrown together.
What's different? Different video card, amount of RAM, hard drive or SSD? How does that add to the assembly time of a system? Each X1000 has the same motherboard, processor and chassis (white/black), so if anything I would think that would make them QUICKER to assemble.
When building a random cheap PC there are always variables that can't be accounted for unless you are using the same motherboard and chassis over and over again.
How long does it take to mount the motherboard in the chassis? Mount a hard drive? Plug in some RAM and a video card?
Now, the software portion of the process might take some time, and apparently the shipping process, but I imagine you guys have done a lot of AmigaOS 4 systems. Since the variables are so few I would imagine you guys would have the process down pat by now.
Unless the failure rate of motherboards, CPUs or the other components is high it really shouldn't take that long to assemble and install the OS and drivers.