Nintendo Switch GBP 37.95

Were they new? If not, they could just be refurbished or open-box returns.
Otherwise, the only reason they should be like that is, as you noted, if they were from package, or if they'd gotten pulled and sold as overstock before getting packaged. Given that Microsoft isn't a company that has to worry about storage space, and the items aren't value-deteriorating with time, that latter option is extremely unlikely. Ergo, your guess is really the only feasible one I see, if they're new.

Of course, bulk-purchasing overstock and then selling the components individually does appeal to some overstocker retailers, so your idea isn't even an unlikely consideration- except, console components take a resale value hit once they're out of box, and it's typically a big enough one that any profits from individually selling should be negated. Perhaps the Xbox One is just in such high demand that that margin [between what a retail and what a consumer is willing to pay for unboxed] is smaller than I'm used to seeing [especially as I typically only keep an eye on older consoles- for example, right now I'm eyeing Wii Us, where open-box seems to trend at 50% retail].

Of course, it's ebay, and offbrand Asian mock-ups of namebrand electronics (and especially of console accessories) aren't uncommon finds. Definitely an auction you'd want to eyeball the photos and received item closely on, to see if there's any minor indication of it being off-brand.