I see it as selling to people who have whole machines that are broken and need replacement boards. From the looks of it you need 6 VRMs for that motherboard (4 for CPU and probably 2 for that massive RAM board), a special power supply, and the original case since that is a proprietary sized board.
Which, again, is why it makes way, WAY more sense for an "enthusiast" to keep an eye out for a whole Dell Poweredge/Compaq Proliant/whatever that's being sold off as scrap to use as the baseline for a toy build, instead of trying to build something up from scratch. You could probably buy quite a few and use the best parts from them all to piece a whole one together for a lot less money than buying the bits piecemeal. (That machine I linked to for $245 had two CPUs, three power supplies, 3GB of rare hard to find memory... you're going to be in for multiple thousands of bucks if you're buying the same as new/unused old stock parts.)
Frankly this "buy the whole machine" strategy is probably preferable for *any* casual hobby acquisition. Someone who's taking the time to take stuff apart, clean, test, and properly describe it is in this for the money. Which I don't have a problem with, really, it's just how it is.
Assumptions shouldn't play any role in sales.
Well, sure, it does. The game these guys play is all about waiting for someone to show up in a panic because they need that *specific* part yesterday to get their business running again, IE, the money they blow on the "overpriced" part is trivial compared to the productivity they're losing to downtime. They're not competing with the guys who just want to clean out a storage unit ASAP and only hoping to get some fun bucks out of it, vs.
paying a recycler to haul it off. The people who pay these prices don't have the option to just sit around and wait for a scrap-priced unit that may or may not have a working version of the part they need to come along.
The very same rusty old car can be a highly valuable restoration candidate or a financial menace that needs to be liquidated ASAP before the city fines start coming in, and it all depends on who's property it's sitting on. Anyone who's ever had to resort to going to a wrecking yard looking for a part they can't find anywhere else can testify that most of the time you won't be paying a lot less for it than you would have if the part were brand new. Maybe you might even being paying *more* for it. You in fact might be paying more for it than the wrecking yard paid for the whole car you're wrenching it off of. You're doing it anyway because you don't have the time to wait around for someone to wreck a car just like yours under circumstances in which you can swoop in and buy the whole carcass to pick it off of before selling what's left to the same wrecking yard.