If its a major OEM machine like dell/lenovo/hp, there are OEM specific keys in the BIOS. This is why they use manufacturer cd's and not retail ones (fairly certain you can't use microsoft downloaded iso for an oem, but correct me if wrong) You need a certificate component, the bios slic strings, and a OEM key off the coa: http://www.squidworks.net/2015/03/how-to-windows-7-oem-activ...
Point being, if the OEM stopped providing the discs and he only charged to cover costs of the medium without profiting I fail to see Microsoft's logic here.
EDIT: I stand corrected, they weren't selling these discs for a quarter as articles reported.