Windows OEM can be *very* cheap, depending on reseller. Point is OEM shouldn't really be sold separately to consumers at all but only bundled with new computers (this is the very definition of OEM), but some does this anyway. Hence there are no real trustworthy comparable list prices on this, you have to search to find the best bargain, there can be big differencies. There are however restrictions in OEM versions of windows when it comes to upgrading the computer (new motherboard/CPU etc); the OEM Windows is kind of similar to the MorphOS license in this regard, it's tied to the HW it's supposed to be bundled with. My brother built himself a new PC (put it together from selected components) and tried to install his old OEM on it, but product activation failed. But then he simply called the support by phone and said his computer had broke down and the seller had replaced some parts because of original parts no longer existed (playing ignorant), and somehow MS support opened it up so he could register/authenticate windows on his new HW!
I understand OEM very well, thanks. Microsoft actually allows the sale of OEM Windows from their normal System Builder channel to other "system builders" as long as the package remains unopened so that they can accept the license agreement. This is why NewEgg and other major retailers can sell OEM Windows with no complaints from Microsoft.
There certainly are list prices and typical selling prices for OEM Windows obtained through the System Builder channel. If you find copies of OEM Windows for sale at a substantially lower price than say NewEgg then one of several things must be happening:
1 - it's counterfeit (a VERY common occurrence from fly by night vendors)
2 - vendors or OEMs are starting to dump existing inventory in anticipation of a new release (Windows
2 does happen, especially from major OEMs like Dell, HP and Lenovo, but I'm not so sure buying a license sold to Dell for installation on a non-Dell PC is valid. If you care about having a legit license then you might be concerned. If you only care that it activates online and passes validation checks then you might be fine.
Yes, an OEM license cannot be moved from PC to PC according to the license. Same thing if a motherboard is upgraded. If the motherboard is defective and an exact brand/model replacement in installed the license is still intact.
However, like you said, Microsoft is very leanient - I've never heard them deny a license activation unless you specifically tell them you're doing something against the license agreement. Typically they ask only how many PCs the license is installed on - if you say 1, they will give you an activation code.
